Local shop has some 2012 clearance CX in 56. I won't race cyclocross, just messy winter rides on pavement & dirt roads
Match the top tube not the 'size' which is seat tube , tippy top of the seat tube..
Since you are not going to Race Cross, even a Hybrid will do... just will have Flat Bars.
and just take a test ride and see.. 1st hand..