This will likely only be of interest to folks around Greater Vancouver/Fraser Valley. My gf lives in Belligham WA so I am down there regularly and they have a gen-u-wine hardware store there- Hardware Sales on James St. (just down from Trader Joe's). It's really a small industrial supply that caters to average folks as well as the pros. Their stock of fasteners is, by regular standards, astounding, just about everything from wire gauge screws to 1 1/2" cap bolts. (Some LH thread stuff, too.) And all individual, in bins- no plastic packages 
A couple of days ago I was there, looking for an oddball screw that I figured was 6-40 thread (#6 NF, which is used for the forend cap hanger on my Chiappa Alaskan TD, in case anyone wonders.) I thought I knew the fasteners section pretty well, but doubted they'd have that. When I asked one of the staff, he asked "Is this for a gun? We have gun screws." Indeed they do and I'd never seen them. Not only 6-40, 6-48 and 8-40, but also 5-44, which I think is used on S&W grips. Colour me gobsmacked.

They also have 6-40 taps (taper and bottom), so I picked up one of those to clean up the threads on the forend cap hanger bar. No 6-48 or 8-40 taps that I saw but I'll check those next time I'm there, although I already have those.
A couple of days ago I was there, looking for an oddball screw that I figured was 6-40 thread (#6 NF, which is used for the forend cap hanger on my Chiappa Alaskan TD, in case anyone wonders.) I thought I knew the fasteners section pretty well, but doubted they'd have that. When I asked one of the staff, he asked "Is this for a gun? We have gun screws." Indeed they do and I'd never seen them. Not only 6-40, 6-48 and 8-40, but also 5-44, which I think is used on S&W grips. Colour me gobsmacked.

They also have 6-40 taps (taper and bottom), so I picked up one of those to clean up the threads on the forend cap hanger bar. No 6-48 or 8-40 taps that I saw but I'll check those next time I'm there, although I already have those.