I prefer to select the parts for a project based on what has worked for me in the past based on fit, function, and form. I do not mark up the cost of parts, and there are certain parts that I will not work with. Here is a partial list of my preferred vendors. They are good people that I am happy to do business with.
Kart: NM Barrels and Bushings
Wilson Combat: Ambi Thumb Safeties
EGW: take your pick, its all good
10-8 Performance: Flat Triggers, Slide Stops, and Grip Screws
Smith & Alexander: Grip Safeties and Mag Wells
Dave Berryhill: Hammers, Sears, and Disconnects
Michiguns: Extra Stout Plunger Tube
Mil Tac: DGW grips.
Legacy Custom: Mainspring Housings and Magwells
Greider: Slide Stops, Triggers, Mag Releases
Chip McCormick: Power Mags
Kart NM Barrel, EGW HD Hammer, EGW Barrel Bushing

EGW Grip Safety & Wilson Combat Ambi Thumb Safety

Greider Trigger with Debris Cuts

Mil Tac Grips with Drake Logo
drake@drakesgunworks.com