For an e-switch? Nowhere. Well, you can get, say, the driver-only for the SP10 from Sofirn, but that’s for an AA light. I got a few to try fixing a TK05 when I thought it was the driver going mental, but it was the LED. So I can always use these drivers in, say, a lantern project.
But any drivers that have an associated e-switch have to be put together in such a way that the switch is perfectly aligned under the hole where the switch-pushing-thingy goes. Add a charger, too, and, like I said, forget it.