The aluminum tanks I've experience with dont use the single backbone frame like on qrs. the hot water/air pressure maybe the only option. Unless you have fabrication skills.

Trx250r 6 gal tank, older style 5.2 gal tank in the flyer





The Zilla in my avatar uses the banshee tank with the C&J Roll frame



No aftermarket options for the lt500 250 that I know of

This flyer is way old like from 1989... So the phone # probably won't work!

I had a few customers that bought those nice looking 5-gallon tanks for their TRX 250 R Honda desert racers around 1990.  The tanks would never go more than a couple races before the tank would split the welds along the bottom seam. 

Fuel tanks that have welds along corner where two planes meet, will eventually crack.  Tanks flex along the seams or intersection of two planes.  Welds should never be placed where the majority of the flex needs to occur.

Tanks that do not have any flat sides or corners that have any 90 deg. corners will be the most durable.  Properly designed tanks place the welds so that they are in tension or compression and never where they are bending as the flat panels are attempting to assume the shape of a round tank as the fuel sloshes aroung inside the tank.