There'a guy selling short action magazines on fleabay for $42.50 with free shipping. The seller's ID is sportshollowguns and even though the title says 3 rounds, the description down below says it's a 4 round. Mine came today and it's an exact factory match - not like the other auctions wanting almost $70.
However, if you don't have a Tikka T3, it's a moot point . . .