Old jack seal kits

[SLONG1958]

I've found a post on here from hiball on rebuilding import jacks and the one I have is different that the one in the posts. I mainly need the big oring or what every you want to call it on the ram end. Just need some advise on where to get the parts
Thanks

 

[sublimate]

http://www.grainger.com/category/rod-and-piston-seals/hydraulic-seals/hardware/ecatalog/N-9al