John, you can get a battery tender and small solar panel for very reasonable. There are a few different makes and models available.
There has been a bit of discussion around here on batteries which others have have included the use of battery tenders.
Here is a link to the Delran website where you can do a little checking HERE:
Solar - Products - Batterytender.com As you will see the company's list pricing and it's not all that bad. You can find better deals shopping around online.
Also, up in your area there is a Batteries Plus store which I have purchased batteries at. Their pricing is very competitive and they offer a nationwide warranty. Their link is HERE:
Battery Stores in Idaho - Batteries Plus
Additionally, I will add a direct link to their multi-battery tender page HERE:
http://www.batteriesplus.com/product...Battery/1.aspx