Pep Boys has the Champion labelled 29HM850CH marine deep-cycle battery on sale for $71.24. Online only, but you can then pick it up in the store.

This is the same battery as the Everstart Maxx 29 except it has only a 12 month warranty. Well worth the savings to give up the warranty IMO.

https://www.pepboys.com/champion-mar...618?quantity=1