When U bring up the topic of new rubber feet, this
seems quite pertinent. I sold an HP-25C to a happy buyer,
but in noting that the unit was well-worn, one of the
most worn portions was the feet, and I wished there was a way of replacing them.
So far, I have just felt lucky and thankful, everytime I buy a used HP-34C and the feet are in pretty good shape. But perpetual hope is not the way to build a railroad .
HERE's my suggestions:
1. If there are units that have ivory feet (hp-25C) then be willing to substitute black material. That is, always go with black, even if it wasn't originally. That type of alteration is too minor to perceive, and it avoids trying to locate oddball colors.
2. At least some products could use ordinary "3M" rubber feet, which are extremely mass-produced, stuck to the bottom of millions of items made currently, and available from Digi-Key etc etc in many shapes and thicknesses.
3. Even if you could locate the material (a sheet or roll-stock) I doubt you could cut it acceptably by any
manual method. It would look terrible. You need a cutting die that cuts under pressure.
4. Expecting that you CANNOT get a suitable match, and noting that the original feet were die-cut, here is what I personally would suggest doing........... Go to an authentic die-cut shop (they make labels and other cutouts on roll-stock) and PAY THEM to make authentic rubber feet. The problem is your tooling charge. Well, they might want $400 to prepare dies that cover a variety of HP calculators. Well, make sure that the top 10 HP applications are covered, thru a variety of die sizes. NOW, find 9 buddies who feel the same way, and split up the costs, so its only $40 each, and now you have got rubber feet.
I can't think of anything else on this subject. Maybe somebody else knows where to buy an authentic exact match without creating it full-custom.
It would be fairly trivial to locate the bulk (sheet/roll) stock, just by asking a rubber foot vendor to part with some material, or locating it as a commodity. The problem is cutting it up.