Where to buy replacement cartridges

[awarsoca]

Sorry if I overlooked this in the Search, but I didn't see it.
Where can I buy replacement cartridges for my Pentair C&C+ 320?
I want to get my second set while I have the "spare" cash (c:

 

[rastoma]

Probably a hundred different places or more.

Did you type Pentair C&C+ 320 cartridge in Google?

 

[awarsoca]

I did. That is why I asked here. There were hundereds of places. I didn't know if there were OEM or after market differences in the cartridges. It looks like $180 shipped is the E-Bay price but I didn't know if there was a better price or if one of the foks here was a better source for the purchase. :-D