I've had good luck with the rebranded
Deka AGM batteries that Advance Auto sells. The size that the EX500 and VN750 use end up being ~$50 after coupon code. They're not much more than the cheapest ones you can find, and you can go get them locally instead of waiting for shipping.
For whatever it's worth, they list the YTX7A-BS for the '08 and the YTX9-BS for the '09-'12. They have an ETX9 to fit that one. I'm sure someone else has better information, but I think you can swap them by just removing a spacer or something (possibly have to mod the battery box a little).
Deka's batteries are rebranded and sold under multiple names. I've seen Magna Power (what AA sells) and Big Crank listed. I wouldn't assume each and every ETX9 is a Deka, but it's quite likely if it looks identical other than the sticker.