Your best bet is to hunt through pawn shops and gun shops for the used gun. otherwise buy the t3 lite new and break it down. you won't find just an action, I don't even know if they can be bought separately. Mine started as a t3 lite 2506, and its being worked over into a nice customized 2506. A base rifle will be 4-500.
I'm guessing you already checked and decided against it; but, it case you just didn't see it, I'm selling a blued Tikka T3 223 for $475 shipped and insured at my expense.