I'm using a 7.5 amp variac (variable transformer) with my Pavelle 401. I rewired the cord from the head to a standard 3-prong type to fit in the socket of the variac. The rewiring job wasn't particularly difficult -- the old cord was pretty shot anyway. One thing to watch out for is that if you set the output of the variac too high, you'll blow the bulb(!) Variacs are readily available on e*y...
BTW, one additional benefit of the variac is that you can vary the light output without moving the f-stop off of its optimal setting. This also works with incandescent bulbs, but there could also be a color shift that will affect VC papers.