Does anyone know where I can buy straps that attach a sleeping bag to a camping or hiking bag

Try Dicks is sporting goods.

Gander Mountain had that when l was looking for it.

wal mart has them.

Just use bungee cords. They have a million uses around camp too.

Bungee cords and D rings from the Dollar Store.
They are great for other uses too, and you know you do need multi-use equipment.

l have used my bungee cords to hang stuff from trees to keep ants out of it!!

Bungee cords ,line ,rope, lol- ducktape.

l dont' know if they make specific straps for that. but i'm willing to bet that if you go to wal mart and maybe even dollar stores you can get elastic clips that are made for holding sheets on the bed and that would work. if not sorry! but it sounds like a cheap way to try and just might work!(:

They're called compression straps, any outdoors store has them, or try Campmor (not sure of the spelling) on-line.