I‘m looking for a supplier of small screws (probably custom machined) that can remain non magnetic in high fields 5-10 tesla or more. My original material was colsibro but I believe there are other materials that can be used.
Stainless steel screws may be your answer. These are generally non-magnetic, strong and can usually be found in most hardware stores and won't rust. Of course you will be be paying more for these special properties but it sounds like it is well worth the price.
Sound like a job for 304 Stainless Steel. Try google.
Any supplier that has aluminium or even some stainless screws. What is the projected load? Would teflon screws work? If it's simply cover panels, teflon screws .or even re-usable rivets would be the ticket!