I started riding about 15 months ago and I have discovered that, perhaps atypically, I am more comfortable in a very flat and forward position. My current 61cm road frame has a shortish top tube that forces me to shove the saddle all the way back on a 20mm setback post even with a 120mm stem in order to have a comfortable reach to drops or my Syntace C2s. That, combined with a 73 degree seat tube, means that my hips are rolled back to the point that anything over say 50km get a bit uncomfortable.

I'd really like to try riding a Triathlon / Time Trial geometry frame to see if it would suit my style and body geometry. The biggest problem with that idea is that I live in the middle of nowhere, where the few LBSs around are overwhelmingly MTB centric and even the one Felt dealer would have to special order a Tri bike. That means that I cannot simply rent one and see. And, since the various Tri/TT bikes from Felt, Cervelo, QR, LiteSpeed, etc. seem to almost universally be carbon competition bikes with matching price tags, I cannot afford to just buy one to see how it fits.

So, my question is: what affordable frame/bike models exist with 78+ degree seat tubes and long effective top tubes? That is to say, when searching eBay or craigslist or the like, what model lines should I look for? Thanks.