My pals who play concertina also use the Anglo style concertina. I do know several people who picked it up in their adulthood! If you are into Folk Music such as Traditional American, Irish/Celtic & such you will want one which plays in the keys of D & G. They are not easy to find. Then there are some which are fully chromatic in that when you press a button it is one note when you squeeze in & a different one when you draw out. If you are really tied to that keyboard, you will have to spend some time relearning your scales, as they are totally different. Do some looking around at various websites for music shops offering "traditional instruments" (maybe even Ebay) for types, prices, etc. Try to find somebody in your area who plays concertina--ask everyone you know, & at the local music shops. Somebody is bound to know someone. Try out their concertina if possible. Get to a major city if need be & find one to mess with. There is not alot in the way of a method book for concertina, but since you are familiar with music, you probably have a well developed ear. Every Concertina player I have ever known plays by ear.    Good luck!