The in-laws won't encourage me to go to Shenzhen (totally understand), however, I am hoping there's a district where I can check out a few CNC routers, some random machinery, electrical parts, etc.

Realistically like I am buying the knock off of some rotary abrasives and they work better than the original US brand--so I'd like to see a shop that may sell them.

Or for instance I use a lot of #11 blades but appreciate unique blade profiles or otherwise--want to waste time looking at Aliexpress stuff but in a store. Perhaps I'd like to look at some random solid state laser engraving toys or if I'm really lucky--there's a spot that sells rails, steppers, and things I can fidget with later on...

I realize Shenzen has everything, however, it'd be a several day long expedition (wife is trilingual--but there's minimal point and too much effort), and I'm hoping there's a couple shops packed to the brim with random stuff.

Are there any place that are worth visiting in HK that fall in one of these realms or categorizes?
Thanks in advance as I greatly appreciate any ideas.