ALL OF THEM !!
There is a cluster of about 30 shops there… there are also a few scattered in a neighbouring street, look for the adverts in Mong Kok station.
Ask some of the Mini-Z sellers where the nearest indoor track is. It’s in a building opposite the hospital… I can’t remember what floor, but you’ll be most welcome there.
Also get you bum up to Sham Shui Po, Aplui St before you make any major purchases. You’ll have to look hard for some of the more interesting stuff. It’s mostly electronics up there but still some RC gear and it’s cheaper than Temple St.
Learn some Chinese… or learn to bargain hard in the street markets. 🙂