I was rebuilding one last year (the ended up a lost cause cause of trashed clutch packs) but when I was looking I did find gasket kits that claimed to fit the K and A. Supposedly came with the extra gaskets. Didn't buy one, so I can guarantee, but that's how they were advertised. I think some were even on eBay.
As an interesting aside, you can even still buy the new friction discs, but at over $200 per stack (2 stacks per motor) it wasn't worth it to me at the time.