A variac is a handy tool on the workbench, but it isn't very suitable as a long-term solution. It is large, heavy, expensive, and vulnerable to mis-adjustment unless you tie-down the knob somehow.
Line-lump (or wall-wart) power supplies are pretty inexpensive and quite possibly available for free if you are a savvy recycler.
Perhaps beyond your current ability to evaluate, but it is possible that the gadget could tolerate the 34V without significant trauma.
Remember, however, that in addition to matching the VOLTAGE, you must also have a power source capable of at least as much CURRENT as the load requires.