I have about 1700 bags and over 700 different kinds.
The best way to get bags is to contact airlines. It's always fun to get replies from them. Some that I got were really original. The best was from JAT Yugoslav. The representative in Belgrade wrote that due to the war in their country they won't be able to send me any bags
eBay is always good to check. I once sold a bag there for $28! Try also to contact other collectors.
Unfortunately, when I started my army service my collection was kind of put on hold. I'm trying to revive it these days.