I've been looking at possibly getting a garter snake in the future and really like red sided garters. However when I look at garter snakes for sale there don't seem to be many red sideds and they are usually more expensive than the other species. But if I'm not mistaken red sided garters are a fairly common species. Is it simply a matter of most red sideds being captive bred whereas other species are more commonly wild caught, or is there something special about red sideds that makes them difficult to breed?

Sorry if this is a stupid question, I keep spotted turtles but am all new to the world of snakes.