Hi Mathew 189!
When I was backpacking I used to mailorder from Campmore (watch for sales and end of season items). I Jeep camp now so weight is no longer an issue; and gear is cheaper.
https://www.campmor.com/
I haven't bought any thing there for several years so do a price comparison before buying.
Any more I shop for nonstandard camping items any where that I can find them; Harbor freight is a good source for double sided imitation Velcro strap.
https://www.harborfreight.com/
(can, also, regularly get a free flashlight; with coupon and purchase)... making a trip to the local store today to get a large Apache case, a smart battery charger and a free flashlight... warning be careful they have a lot of worthless junk... they are my favorite place for silver (heavy) ground tarps; think that I got the last bundle of nail type tent stakes there... cheaper than wallymart..
Amazon has gotten a lot of my business; got a quite nice Chinese alcohol stove there before Christmas, will likely get a one burner butane/propane Gas 1 stove or a commercial (thinner) gas hotplate there, when I get around to it.
REI and other commercial outfitters have almost completely lost me for any thing but looking due to their prices.
I regularly look through the Cabelas catalogue for Ideas and outfitter level stuff; again wait for sales and bargain cave items...
https://www.cabelas.com/
I got my 10x10 canopy and regulary get replacement camping chairs at the local wally mart when they have a sale...(only get the fat people (350 lb. rated) chairs the others give out/collapse too easily; usually with much laughter around the campfire...).
..I regularly hit up the local surplus stores for tent stakes , 550/parachute cord, ammo cans and other small items..
Enjoy!