If you're still on a tight budget, something to clamp a bottle cage around that main frame tube might be the best answer. Or, as that's an awkward shape, perhaps the little short tube where it says "Showdown". Jubilee clips, perhaps - clips designed for ordinary bike frame tubes are likely to be too short, and cable ties not stiff or strong enough. Miss T is right, though - if you care about the frame, put some old inner tube or a couple of layers of insulting tape around the frame before you put the clips round.