Here, There and Everywhere.
I have a LM2596 VV Mod I made out of a Speed Stick Deodorant container. Tried several copper pipe mods, a flashlight mod and am currently rough testing my Boxed VAMO... (Old VAMO died.. so I pulled the guts.. turns out it was only the main switch that died..)
I've ordered parts from Madvapes, Fasttech and various electrical parts companies. Picked up items at Home Depot, Lowes and others, including a dollar store.
It all depends on what your knowledge and skills are on what you can do.
If I wasn't such a 3rd rate builder, I'd be rich.. LOL