My understanding is the Vivitar power supply is there to provide a STABLE output as well as stepping down A/C to a lower voltage.

The only thing it's powering is a lamp which doesn't care AC or DC. If I cannot repair the power supply, I would go with any power supply capable of supplying the voltage (AC or DC) and able to supply sufficient current. I would first open it up and see what blew though. I *think* there is a large capacitor in there that can go.

If you'd like, I can open mine up and see....