Plastic Pants?????

I am having a hard time with plastic pants / waterproof pants. I am a larger person and I am having a hard time finding good quality diapers that have the plastic backing. so i have found decent cloth backing diapers but i find that i have to wear plastic pants with them so they dont leak over time. My problem is i cant find plastic pants that fit right. as well as i find that the ones i am buying rip very easy on the sides after a few uses. can anyone make and suggestions as to a decent pair of plastic pants that don't cost an arm and a leg ( keep in mind i live in canada) or a decent diaper that is made in bigger sizes and has plastic backing (again not to expensive) as well as sizing for plastic pants. thanks for your input in advance.

Plastic Pants?????