Yes that is probaby the best solution... if I live in USA.
Belive it or not, those inserts are considered by law "firearms parts" so you can not import them and if you bring them with you from USA, you commited a crime!
The option to make my own inserts is the best to make usable a fantastic shotgun that, besides the damage inside the barrels, are in really nice condition.
So, I still need to know, what steel to use (I know 4140 is the forum recomendation, but I can not find them here).
The OP is in Mexico. He is honest, and law abiding, and as a direct result of that, he has been targeted by virulent leftist Mexican gun laws. Had he some street cred with one of the larger cartels, Eric Holder and Barrack would have personally seen that he had access to anything he wanted, but, that privilege will go to others. Too bad.
Suggesting he acquire a part to fix his gun is a no-no. He can’t. So, well intentioned that anyone who has posted on some nifty part that they can buy of eBay, or, wherever, is doing him exactly no good.
Make note of it. You ain’t in Kansa anymore, Toto. Americans always believe their gun laws are the only gun laws. Not so.
Guess I’d shoot for measurement and cleanup, which, if he is talking about producing a part on his own, he should be pretty close on equipment.
Good Luck, Jose’