I was thinking of making up some custom cannonball tanks like the one I made for my speed demon race bike. It's a 6" sphere and holds 1/2 gallon. I can make a universal seatpost mount, hanging frame mount, or, if you provide exact dimensions, custom mounts. The major impact on cost is the filler bung and cap. Those ain't cheap. I'm thinking price would be $150, with free shipping in the USA. Gimme some feedback, let me know what you guys think. My original tank pictured. Mounts, filler, and petcock will differ in production models.