The only people I can think of that may make them out of stainless is:
B. J. Engineering
Unit 2, Worcester Enterprise Centre
Shrub Hill Trading Estate
Shrub Hill Road
Worcester, WR4 9FG
Phone or Fax 01905 29517
Mobile 077 104 01827
They make everything for beekeeping, mouseguards, castelated spacers, queen excluders, roof covers etc...
Why are you looking for stainless wire construction, what benefit is claimed for them? Not sure that I agree with you on this? I had a wire one that came with some second hand gear and the wires could move (warped wood) and possibly then not 'exclude', I suppose the supporting frame work is the key thing here. The slotted metal ones (I am told) can cause damage to wings (thats what I am using at the mo) so I was working on the basis that a plastic excluder is better because they dont warp and are smooth reducing wing damage - even though they may have a shorter life
The zinc slotted have a burr on 1 side which can't be very good for the bees. I looked at a plastic 1 from Thornes the other day and that seemed to suffer the same problem. Wire excluders come in different qualities the best being the Herzog. If you google 'Dave Cushman' you will see some drawings of the different types. I would prefer them to be stainless steel so they won't corrode.
I've got some wire unframed Hertzog excluders made in the early 1980's they are still usable. I think stainless steel would be a rather expensive solution to the corrosion problem. It would probably be better to replace the excluders when you have a problem with them.
I have one wire QE which I only use when I've run out of the slotted ones. We had a queen that always managed to get through the wire one - christened her Twiggy! Tried a plastic QE once. The bees built brace comb and gradually managed to warp it (in combination with hot summer?) until it resembled a mountain range! So, I now stick to the slotted ones, which are also quicker and easier to clean.
The Herzog excluders were the best available. Unfortunately the company has ceased to operate.
If you want wire excluders it is best to get them from a company in the USA. Dadant or Mannlake have good quality items.
I use Thornes and at only £7.04 + vat it's a steel pardon the pun!
Wire Queen Excluder
Queen excluders are vital pieces of beekeeping equipment and do exactly as their name implies. They exclude the queen from parts of the hive as and when the beekeeper requires. This is because the queen is slightly larger than a normal worker bee and cannot pass through the slots. They are used almost exclusively to keep the queen in the brood body. By doing this, the beekeeper restricts the queen to egg laying in this one box, leaving the supers full of only honey. It is normally only used during the active beekeeping season and should be removed during the autumn and winter months.
Available for all sizes of hive- National or Commercial 18 1/8" x 18 1/8" (when fitting a national excluder, as it is square, place the excluder with the wires running across the frames): WBC 17 ¾" x 16 ¼": Smith 16 3/8" x 18 ¼": Langstroth 20" x 16 ¼": Dadant 20" x 18 ½"
The wire type is probably the best type of excluder available and is made from coated steel rods (2mm diameter) accurately spaced at 4.3mm. They all have a wooden (pine) support frame, which provides a bee space on one side, and flush on the other. In a National, WBC or Commercial hive, the excluder is fitted with the bee-space on the underside ensuring the bees have free access over the top of the frames through the single bee-space created. On a Smith, Langstroth or MD hive the bee-space is uppermost and the flush side is placed onto the brood body thus maintaining the single bee-space. If the excluder was turned over the brood box would have a double bee-space and the bees would soon fill this with brace-comb. (This is comb the bees build between gaps of more than a bee-space. Gaps a lot less than a bee-space are filled with propolis). The wooden corners of all wire excluders are half-lapped, glued and stapled. The wire grids are held in place by black japanned gimp-pins that are clinched over to ensure a firm hold. By using this type of excluder you will minimise wear and tear to bees wings and bodies. They are generally stronger than the slotted type of excluder and should provide years of service.
National grids are available separately 17" x 17" for those who wish to make their own frame.
National grids are also available in approx. 18" X 18" for those who just want a plain, un-framed full size wire excluder.
I use wire queen excluders, one from National Bee Supplies, the other from Thornes. (the slotted ones ain't much use with top bee space) the bees in one of my hives are building a little bit of brace comb on the Q/E, but none at all on the other hive.