Yes they do. I have installed a few kitchens using RTA products, which included a fridge cabinet. The items were obtained from a local company called Busy Beaver. I have also built cabinets, using either plywood and veeners, or premanufactured panels such as this:

http://www.instockkitchens.com/georgetown-cherry-maple-discount-rta-kitchen-cabinets/ref96-georgetown-rta-96-quot-refrigerator-end-panel/prod_2667.html

The fridge surround is sometimes built without a back, basically being two sides and usually a separate cabinet placed overhead. It is built to size after the fridge is chosen.

Another alternative is to purchase a RTA "pantry" cabinet. They are usually 24" deep, but because they ship disassembled, they are fairly easy to first modify.

Talking to the salesperson, you should be able to bargan for less than the advertised prices, because you won't need all of the multiple shelving or doors found in the completed units.

http://www.extremekitchen.net/store/tallcabinets.html