your best bet is one from a truck mounted camper or build a new one. The problem is the darn window, it leaks
and rots out the wood. I build mine from a cut down interior door (plywood not partical board from a reuse center) from a house which I laminated white Formica to inside and out. I reused the aluminum trim from the door. For a window, I used a 12" round portal window for a van. I replaced the door lock with a Fastec and sold my old one for $150. The old lock is a Bargmann L400 and are rare and in demand.