Lil' Sparky, those disconnects from MC are compatible with Parker Moldmate series. You might check with Parker (I found them via google) to see if replacement o-rings are available. I bet they are.
Meanwhile, can anyone tell me if the barb fitting at the back of the female disconnects can be removed? For example, on 6739K64 1/2" NPTF female coolant hose quick disconnect (straight), is it possible to unscrew the barb off of the disconnect? And is it 1/2 inch NPT or NPTF if so?
Finally, has anyone tried using the high flow parts like these? The plugs and the sockets come in male and female genders so you can adapt easily to whatever you have, male or female NPT fittings, without additional connectors. You can add the brass barbs. It works out to be about twice as expensive as the other fittings that everyone is using, but it has some advantages. They seals are Buna-N and are only rated to 250 degrees, not as good as the silicone seals in the coolant disconnects, but still usable.
5346K25 Brass Barbed Hose Fitting Barb X Male Pipe for 1/2" Hose ID, 1/2" Pipe
6537K93 High Flow Straight Through Hose Coupling Brass Plug, 1/2" NPTF Male, 1/2" Coupling Size
6537K13 High Flow Straight Through Hose Coupling Brass Plug, 1/2" NPTF Female, 1/2" Coupling Size
6537K65 High Flow Straight Through Hose Coupling Brass Sleeve-Lck Socket, 1/2" NPTF Male, 1/2" Cplg Sz
6537K75 High Flow Straight Through Hose Coupling Brass Sleeve-Lck Socket, 1/2" NPTF Fem, 1/2" Cplg Sz