a friend of mine (Trapper John md) told me about your request, so I decided to join this forum to answer you
I replaced the original 110V transformer by a ring core trafo, which is attached at the bottom plate (I used one of the screw holes of the original transformer).
You will need a 2x22V or 2x24V with at least 30W power, which you can get here e.g.:
http://de.farnell.com/block/rk40-22/tra ... dp/1419543
After that you only need to adjust the output voltages to +/- 15V with the trimmer.