1) farnell or rscomp singapore, order over the net(depend on availability)
2) stake out simlim tower(germanium transistor not much thou)
3) order over the net with smallbearelectronic, mouser, banzai electronic or loads of other which deal with geetar effect/audio electronic
anyway, soemtime the pedal is really not design for different transistor(npn, pnp, silicon/germanium) swopped in out and still work. Either no sound or bad sound and worse still, damaged transistors etc.
instead of just looking for germanium one, take note of the existing transistors in the pedal, search for other model, within the same family, you might like to get those and try out.
The slot for the transistors on the pcb can be replaced with component socket, so you can just snap in different transitors to test, while taking note of the pin out of the original and replacement transistor