Deka makes the batteries for HD and are a lot cheaper. I have a place near me that sells the Deka ETX30L(the model for my bike) for $108. Last I checked HD wants about $165 for the same battery with HD on it.
Some things are simply not worth the hassle. I've only had one HD battery replaced, and I went to the dealer. Took the old one in, got the correct replacement, and was done with it.