Always ordered mine from Nengun in the past...they're good for about 25,000km so 1 a year would be more than enough for most people...
I'm sure Just Jap or similar would sell them...Never really checked. A trader on here (Kudos maybe) also had some at one stage....I might have even got my last one off him come to think of it...
Blitz also sell a non oiled panel filter, but I've never used it personally.