I can reccomend two companies that have excellent "off the shelf" shoulder systems for your friend. And best of all, no wait time and most of them are under $100, which I know is a concern for our service members. Try Galco's excellent "Holsters for Heroes" program!!! When one holster is purchased, they will supply and additional 2 holsters to servicemen at no cost! You can read up on it at the link below. Their holsters are VERY good for "off the shelf" and in fact I spoke with some Marine V-22 Osprey Pilots last year at Ft. AP Hill on training and two of them were wearing these!!
Also try El Paso Saddlry in TX...they also make some excellent products and they still make an excellent version of the 1942 Tanker Holster, which would work very well for your friends purposes. I have an original Tanker from the Korean era and use it from time to time on my 4 wheeler..keeps the weapon secure and out of the way. Best wishes to you and your friend and THANK YOU BOTH FOR YOUR SERVICE!!! GOD BLESS YOU!--John
http://www.usgalco.com/Holster4Heroes.htm
http://www.epsaddlery.com/c-9-holsters.aspx