Meh, I just buy remanufactured cartridge from a no-name place. It costs me about $50 shipped for a high-capacity cartridge compared to $!20+ for the equivalent OE.
A refill kit runs about $30 I think, and I'd rather spend an extra $20 or so on something that has a warranty.
Reminds me of the rebuild your own brake caliper vs Chinese remanufactured unit debate.