Welcome to geekhack!
It's a shame you can't find a keytronic. I just came across one yesterday for $1.99 at the local thrift store. Poked at it for a few minutes, and it was actually quite tactile.
So, I'm not sure what your budget is, but you could try to snag a keytronic, look into a Topre board, maybe a fujitsu peerless would be worth looking at, or check out the Cherry MY keyboards, such as the G81 (I believe that was the number).
Most of those options should be relatively inexpensive, except for the Topre. Which isn't really a membrane, but is a rubber dome. Sort of. Super nice though, and I think if you're willing to shell out the quid (can I use that term that way?), well worth it.
Edit: the link works for me. Likely a phone issue.
Edit 2: Oh, and check out the "Blue Cube" (it's in the wiki). If it works for a model M, I imagine it can handle your MS internet keyboard. And hella cheaper than a new board.