Many gun shops can do it, but often use ####ty (IMHO) Colonial chokes. Depending on the barrel, you may not be able to do what you want. You need to measure the inside of the choke area and the outside diameter of the barrel. Some barrels are too thin and there is not enough meat to install the tubes. Briley in Texas can do it if anyone can. Steve Milton (Precision Arms) in King City, Ontario may also be a good option.