Sounds like you need a "tidy tank" (or equivalent). It's a fuel tank that can slip into (or out of) a pickup truck bed.

Here's a link: http://www.tidytanks.com/origtank.html . These types of tanks are not hard to come by. Lots of people who live/work in the country have them. They don't always transport them around; put them on railway ties, well away from buildings. You can even find them used at auction.

The question, though, is: do you live in an urban or rural area?

Storage of this much gasoline in an urban area may violate all sorts of fire codes.

If you are in the country, though, you can get a local bulk supplier to top off your tank (on site) with a phone call. Very convenient.