These are keshi figures. They came from gachapon machines in Japan. There were several series, from Super Bomberman 2 through 5, Saturn Bomberman, and more... The ones you're looking at, from the Super Bomberman 4 Guidebook, have been painted. You'll likely be buying unpainted ones if you can find them.
Places like eBay are your best bet. People sell keshi there all the time. It's just a waiting game, really. My own collection has taken years to amass, and I'm still collecting. You'll have to fight me for any that I don't have, though. :P
Here, I have Jet Bomber and Great Bomber. This is what they look like. In my hand, you can gauge their relative size.