There are several cel dealers that either carry
bags on their site or have carried them or have
sold them at cons.  You might want to try checking
out Noriko's or Usagi's House or asking around (as
I'm sure there are some I'm forgetting).

In the past I've gotten bags from American
Plastech (http://www.americanplastech.com) and
Heiko, Inc (http://www.shimojima.co.jp/heikoinc/).
 I've also heard a few people recommend ICON
(http://www.iconusa.com).  This topic has come up
several times so you also might want to search the
archives for more information. :)

I know at least American Plastech and some of the
bags from dealers come without self-adhesive. 
There are probably more out there at the other
shops as well.  I've had good luck with bags made
of polypro and they're generally quite inexpensive.

Keys