I would send it to one of them and have them look at the gun and give you a price to fix it right. They have a better chance of finding any part that you need and making the gun right the first time. It might not seem that it is the cheapest way to go but most likely it is. NID parts are not that easy to come across and any gunsmith that has a stash is not very likely to sell them cheap as they know replacing them is getting harder to do all the time.