It's been about 5 years since I've been to Osaka,
but Panic Media Mix (in Den-Den Town) might still
be there.  There was also Anime i-land (in Umeda,
I think), and there was another store that had
some cels right across the alley from it--might
have been Amusement House Liberta.  I have no clue
if the latter two stores still keep physical
retail shops open.  It's best to find their ads in
Newtype/Animage/etc. as they tend to have a map if
they're still in business.

http://www.panic-web.net/
http://www2u.biglobe.ne.jp/%7Eiland/
http://liberta.cn1.jp/