I think 700c is pretty much off the table at that size. Maybe look for something with 650B or 26" wheels. I took a look at the (26") Surly Long Haul Trucker but that's still got a 50.5cm TT and a stupidly steep seat tube angle.
Serotta Colorado III Track (Renyolds Ouzo Pro Aero Fork, Dura-Ace to Mavic CXP-14 wheels, Sugino crank, Thomson and 3T the rest), Steelman Cyclocross (Campy Record 10, Deda Newton & Thomson stuff)
Not sure what your time frame is, but you can get some good deals in used stuff in smaller sizes. Either the frame will have no buyers and you'll get a great deal, or you'll end up fighting to the death with some other short person for it and the price will get a bit much.
I recently got a ~48cm Steelman Cross frame on ebay for $1,500 for a complete bike, and I came across a few other frames/bikes in the 48-52cm size as I was looking.
Can anyone thing of a cross frame, that isnt custom or mad expensive, that has a top tube under 50cm?
Not with 700c wheels.
What's your current road bike? My special lady has a longer top tube on her cross bike, she just uses a shorter stem, no problems.
If it's really unmanageable, then look for an XS mtb frame and rigid fork. The top tube will in actuality will be longer, but the geometry is more feasible. A full range of frames and forks are out there. Might be slightly overbuilt for cross, but rigid 26er is a fun way to ride over all but the rockiest terrain.
Marin Pt. Reyes, Gary Fisher HiFi Pro, Easy Racers Gold Rush recumbent, Cannondale F600
I'm a small guy (5'3") and always have a bear of a time finding a bike in my size. Am also looking for a CX bike, and the 2009 Marin Point Reyes looks promising. It's more toward the MTB end of the CX spectrum, equipped with flat bars and 26" wheels, disk brakes, and carbon fork. The top tube on the 15" frame size is a bit longer than you want though (54cm). Not particularly cheap at just over $1K list, but weighs just under 25 lbs.
she rides the 650c cannondale femme something or another with a 49cm t.t. I think? and like a 44 or 45 s.t. Getting down to just maybe saying wtf and getting the 24 redline but trying to find other options. I have searched extensively. I wish some of these companies like alan and cannondale would make a cross frame in the same sizes they are flexible about with the road frames. sigh.
*also might I add that even if some of these bikes have a ''50cm'' top tube, it usually isnt the effective length so a slightly smaller stem would not really help her reach out, alot of the 50cm top tube bikes are running with like a 52cm effective. just fyi.