I've got a couple old road bikes, and I was thinking of building one into a fixed/single (flip/flop setup). It's slim pickin' around here for stores that cater to this...are there any online stores that sell to this crowd?

Similar note - can anyone recommend some components for this project? I'm looking to buy everything except a frame, but this is my first buildup project and I'm not especially brand-savvy yet, so I don't know what's out there.

https://sheldonbrown.com/harris/fixed.html
https://sheldonbrown.com/harris/singlespeed.html
https://www.nycbikes.com/
https://www.businesscycles.com/trpix.htm
https://fixedgear.americancyclery.com/

Also, these two outfits occasionally have something I can't find elsewhere.
https://bikepartsusa.com/
https://www.danscomp.com/

I'm still hoping for someone to come around and sell Velosteel coaster brakes.

also try www.spicercycles.com gene is awesome.

https://www.worldclasscycles.com
https://www.aebikes.com
If it's just a road conversion, buy a good pre-built track wheel, such as a surly/ma3,
or a promax/open pro, and use a cheap front wheel and use old road cranks. You can really do it on the cheap. Make sure that you use a GOOD COG. using a cheap cog will ruin your hub threads, thus making the hub worthless.

https://www.bikecult.com/works

bike works is good, too. just don't get the sovos wheels.

I have accounts with a few US wholesalers. I hate doing small orders as the freight is a PITA, but if anyone wants anything, feel free to drop me an email and I'll see if I can't help out.