Some of the gas cylinder manufacturers will be hydrotesting products at pressures higher than this. If your device is small enough, you might try asking to hitch a ride.
They may be able to point you in the right direction. Or if this is an ongoing problem, they may be able to provide a tester with a higher pressure capacity.
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
Now that you've mentioned the size and it's pretty small, I can say that most hydrostatic testers could easily handle it.
All pressure vessels must be tested regularly. Fire extinguisher companies have to hydro test extinguishers. The tester would have no problem dropping your device in and accurately running up the pressure. This could be more convenient for you especially if several repeated tests are required. Most towns have at least one fire service company.