There is no spare wiring (future expansion) wiring in the car. You could scab into an existing circuit like the Coil. Although the Halo leds don't pull much wattage its never a good idea to borrow from an existing circuit.
Years ago I was taxiing a Biz Jet to the run-up area and flipped on the Freon A/C. The Compressor light came on and also the Gear Unlock light. Scared the crap out of me. After reviewing the logbooks I found someone had installed the Freon kit "using existing spare wiring". Luckily for me it was only the indication panel and not the hyd control valve as well.
I'd add a new circuit and a toggle switch, but thats just me.
I've bought from both of these vendors without any ill issues.
ID plates for Lucas diameter switches can be found here:
https://www.bits4landys.co.uk/series...s-switches.htm
ID plates for 1/2 dia standard toggles are here:
https://www.cckhistoric.com/shop/Cla...2mm-p112639431