For the record, those are ML switches, which are quite different from the MX switches that most here talk about. The key caps are compatible, though.
And just to mention this, the HHKB is a non-ANSI layout, in case you haven't looked closely at one. Personally, I prefer it, but a lot of people have issues with some of the key placement choices.
You aren't really going to have much luck finding even a used one for under $200. That said, there are a couple available here in the Classified section. The one linked above, and elservo was selling his before Christmas. Not sure if it's still available or not, though.