Does anyone make a cross frame with a 50.5 or less top tube?

How about 650c or 26" (mtb) cross tires?

Is it for a small woman or a child? Either way, kona makes a 24" wheeled CX bike i believe.

Yes... Kona and Redline both make 24" cross bikes... I'm looking for something a little larger because I've found that 4'6" is about max for those frames...

It's likely only a custom frame/fork will work for 26 inch tires. Independent Fabrication has made cross frames with 26 inch wheels before and they work very well. I built up the first models they ever made that way and they rode really well- no toe overlap on a rider with a size 41 shoe and 170mm cranks. The stock44cm frame has a 50cm top tube, and with 26 inch wheels they might be able to go shorter.

Shwalbe makes a 26 inch tire that can be used for cross- it has a pretty good tread and is under the UCI 35mm. Hutchinson also makes a tire that fits a 26inch rim. And Dugast can make 650's if cost is no object......

surly makes the crosscheck with 650s or at least they used to.