Barbeque paint is a good option. Tough as hell, and looks great in its matt black way, without being a thief magnet.
Hammerite or Plastikote can both give really nice, decently tough finishes, hammerite does chip easier than some finishes while plastikote is more likely to swirl or discolour (and it's a bugger to get a totally even finish) but they both work well. Don't waste your time with cellulose or singlepack sprays (such as cheap car paints), they're 3-part systems (under, base and clear) so they're time consuming, the top coat needs cut back and polished, and even with the best attempts, they're still brittle and fragile. Horrible for bike use.
But… Cheap powdercoat is still miles better, and not all that much more expensive.
I'm doing an old frame in hammerite yellow- I'm doing it because I like the project but it makes no real sense… But it's nice to do it yourself, and shooting paint is always a pleasure to me.