A number of gunsmiths install chokes but probably none in Canada are equipped to install Beretta Mobile chokes. There is absolutely nothing wrong with a fixed choke gun if the constrictions are in the ballpark for the intended use, as your extensive experience with trap shooting surely confirms. Your gun is not proofed for steel shot and marking of the bore surfaces is possible with cheaper promo type ammo but most Beretta target guns have chrome lined barrels, harder than soft iron ( so called steel shot ) and should be ok with quality ammo if you simply have the chokes opened to IC and MOD at the tightest. These are your most versatile all round chokes, safe for steel and won't break the bank. Most gunsmiths that do shotgun barrel work price this job very modestly, much cheaper than threading for tubes and then buying the tubes.