I assume your camera has a typical "bare-bones" hot shoe -- or can support it. If that's all you need there are tons to choose from. But the smaller they get , the less power they have. There are tiny flashes that use ONE AA battery, small ones that use TWO -- and have twice the power -- and then FOUR AA batteries, but these are the big ones.
The smaller flashes also tend to have fewer features -- non-auto-exposure, no bounce, etc.
So how tiny/weak do you want to go???? What GUIDE NUMBER meets your needs --10, 14, 20, 28 ..................?????????