[Doug]

I too have some of those belt driven Jouef locos. Mine are also a bit stretched and old and also either prevent the loco from moving or make the running quite bad.

I have not found a suitable replacement, although I managed to shim the motor in one loco, thus tightening the band a little and helping it with traction.

I'll try and enquire at a couple of French shops to see if there are replacements available.