Airsoft is fine. I use a KSC G19 (glock 19 replica) and its known as one of the best. The Stark Arms G19, and WE G19 are also good options. Its ideal if you get an airsoft gun thats a replica of your own gun. I supplement my training with my AS Tool often.
Best bet is to buy online. You will want a gas blow back gun (the slide functions like a real gun).