I have recently been researching them.
best one for Valkyrie is the BikeMaster DLFP-16-BS Lithium Ion Batteries.
higher amp hrs and CCA than the one actually listed for the valk. same size and price.
only better ones are over $200.
best AGM would be Motorcross
https://www.batterystuff.com/powersports-batteries/YTX14H-BS.htmlactually made by Yuasa. can be found lower $ than this site.
Or any AGM made by Deka. My walmart is a Deka, in Aug it was 8 yrs old and still going strong.