Automotive paint and body stores actually sell an inline toilet paper filter cartridge here in the states.
You probably won't find it at pep boys or O'Reilly's, but a real supply house.
Also, 3m makes an M90 spray adhesive that is supposed to be better than the M77. I have cans of it left over from the cabinet refacing I used to do. But, as of yet, I haven't tried it on leather.