Try a company called Zanotti, 123 W. Lone Tree Rd., Cedar Falls, IA 50613, Phone (319) 232-9650.
They make modular safes, which can be assembled where wanted and disassembled if one moves. In the smaller sizes, the pieces can be easily handled by one person.
The safes are pretty good and come in several sizes, and I think one would work for you. Their prices are reasonable. Only problem is that, due to the construction, there is no fireproofing. If you are interested, give them a call; they have no e-mail address or web site.
Jim