Good news ! Leaks can be a ______ !
I would keep the leaking canister and one day run some ultra fine 2000 grit wet dry sand paper on where the o rings sits. It will show high low spots by where it marks the plastic. They use such cheap plastic now a days to save them money and things are not machined / molded as well today. If its is uneven try an o ring "one" size thicker and you may be able to have a backup if the other ever breaks. To me worth a try or maybe I just have too much free time ?
Some companies will custom make one. I used
http://www.applerubber.com/Back in my restoring days.