Clickteam Fusion 2.5

You could go to G2A

There are still some copies available on barter, and I see a couple of recognizable, reasonable traders on that list.
It wasn't a high-demand offering, and it was tier 1'd twice in a row, so even with a 2 year (and change) gap, it shouldn't have overly high trade value.

I can't imagine a trade for it ending up as anything but much, much cheaper than the prices a quick google search is showing me for grey market offerings for Clickteam. But then, that disconnect is also why we have opportunists on Barter who actively try to get items for cheap so as to resell them.

I can't attest to the preferences of the traders in question, but I personally wouldn't think twice about trading for a wishlisted Humble Monthly game, and would likely be fine with just a simple wishlisted BTA game for the exchange. Maybe that can work as a starting consideration for you. Barter has its opportunists, especially among those who've joined since the site came back up after it went down for a while, but those with non-exaggerated valuations similar to my own haven't ever been uncommon to the site, either.