Bamboo shrimp creep me out. lol. I don't know how aggressive they are, so I don't know if they will go well with a betta. The good thing is that they get pretty big so there's less of a chance of the betta eating it. Your local pet stores might only get ghost shrimp in on certain days of the week, so ask them about it. My Petsmart only gets them in on Wednesdays, and they're usually gone by Thursday. One of the Petcos in my area usually has ghost shrimp all the time. They're ginormous, though, so I question whether they're actually ghost shrimp or macrobrachium shrimp which are more aggressive and might grab your fish's fins.