Free: Contests & Raffles.
Not sure what is local to you, but Kesselring has/had them up at Bow.
Ben's and DJ's can order them.You will pay.
Joe's in Kirkland has them, so did Lynnwood, but they are not cheap for sure. I cannot bring myself to buy one for mine at that price. Sure hop I do not need another!
I bought one for my -06 at a WAC gun shoe. I believe I paid $60.00. You can also get the 5 round clip but they hang below the stock to much for me.