I'd just buy one online. You may not find one for an omega but I'm all but certain the tap is a standard size. Try one off your bow to see if it fits and if it dose then just order one. If it's too long then it can always be cut down to size.

http://www.eders.com/Archery_and_Bow...61-p2,161.html

Eders has a bunch of them.

I have a question though. Dose the string show signs of wear and is he having arrow clearence issues? If the answer to these question is no then it really dosen't make a big diffrence if he has one or not.