While I'd love to plug my own site, the reality is that 99% of my own needs for survival gear are serviced in one of three places:

www.nitro-pak.com
www.sportsmansguide.com
and www.amazon.com (which all my store is is a specialized amazon affiliate store so that's basically my #1 stop)

Beyond that if you can't find it on amazon, you'll probably have to buy it direct from the vendor.