I think it's one of the standard ones. John D. Taylor's Velvet Falernum. I bought it from Weinquelle Lühmann in Hamburg (great store alongside with Spirituosen Wolf -- will miss both of them, they almost always have some of the best prices even in comparison to online shops (ok, there are some online shops that have even cheaper prices.. Conalco comes to mind, I just ordered from them a load a couple weeks ago and it's worked out very well, can only recommend them: Courvoisier VSOP 1l for 30€, Gosling's for 17€ etc.)).
Why didn't you like Forgotten Flavors' one? I've just heard great reviews about it -- mixology, other websites, Le Lion etc. Actually, Le Lion still uses it (I think one of the two founders of FF worked for Le Lion and therefore they got the last batch or so). I liked all their drinks with FFs' Falernum. Next time I'm in Hamburg and at Le Lion I'll try it neat now that I have a comparison.
Actually, I may just write an e-mail to FF later today and ask about some tips and tricks on how to do my own one. I doubt that they'll share their complete recipe though.
Have you tried TBT's Falernum? I haven't been impressed by their Crème de Violette at all (it's just too flabby in taste). But it may be worth a shot.