i had the same exact problem with finding a air filter for my 69 tmx 100 and i couldnt find anything but i still had the housing and all the boots for it so what i did is i just gave up on finding a new filter and just bought a bulk piece of uni foam for a filter and just cut a round piece of it so it fit in the housing part that you take out. it's worked great for me you just got to get some foam filter oil for it. i havnt had a single problem and with out taking it apart to look at it you would never be able to even guess that i did it cause it all still looks original. that's what i would suggest its a cheap and easy way to fix a problem. i just took it apart the other day to check it out to make sure it looks good and it looks like it's all working fine.