The last time I put my pump back in I cut one of the orings. I went to my local hydraulic shop and they gave me something that wasn't the exact size, but it has sealed perfectly. I can track down a p/n and post it.
They were $1.25 for 2 sets of orings.
I may try swapping just the filters first to see if my pump is in fact failing, but regardless I like the idea of having a spare pump to carry for the far from anywhere trips (Goose bay and beyond this summer!).