Your frame is Ishiwata 022 - Not a lot of frames out there are as good as your Trek, but you can look for another frame in 022, or Columbus SP/SL/SLX or Reynolds 531.
Generally any bike utilizing those materials will be well in excess of $200, though occasionally you can snag one for a lot less if you are persistent. Another possibility is a frame made in Tange2 steel - some better eighties Japanese bikes utilized it.
There are a lot of lesser frames that will accept the components- but you may note that they will not ride quite as well as frames from the materials mentioned above.
PS- Part interchangeability is not guaranteed but better once you get into late eighties bikes - the seat posts however are infrequently interchangeable even then.
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