Try Mag-na-Port International they pioneered ported barrels. Fax number is 810-469-0425. I personally hate ported barrels and muzzle brakes as they do too much hearing damage. But recoil is not a big problem with me to contend with.
If you are going to do it, I would consider installing a Vais muzzle brake. It will be less hard on the ears, still should wear ear protection, then the mag-na-Porting and I feel that it reduces recoil better then the porting does.
When I use to do gunsmith work, I installed about 12-15 muzzle brakes on customer guns and found that the Vais was better in recoil reduction and noise then several other common brands that the customers requested to be installed.
RELH