You should have just bumped your
prior thread rather than reposting. Judging by the lack of response you got last time, I'm guessing that many people aren't familiar with these (I wasn't, and I have at least a passing familiarity with the majority of the Allison line).
Your best bet would be to set up an automated search on eBay. I would suspect that the IC20 used the same remote, so you should probably include it in your search.
There is (or at least
was) a Yahoo group dedicated to Allison speakers, you might want to join that. If you find someone who has a set, and the remote uses standard IR codes, it's possible you could have them program a learning remote with the Allison codes.