I've seen some that are expensive, however I also saw a homemade one that cost all of 20 bucks in parts, I believe I saw it posted in GlockTalk a while back. I do have a machineshop at my disposal and really want to make one, however time has drifted me away from it. It really is just better to have a competent gunsmith with a good sight pusher work on your gun in the end. (IMO)
BTW, you are correct, using a hammer and punch on tritium night sights, if done incorrectly or carelessly can break the vials.