I think the bottom metal cost $68, $75 or so shipped. I bought a complete new magazine from a local shop.

HotHolds posted this list of factory part numbers if you prefer to order online vice calling savage... this is for bottom metal only

Order directly from Savage if you can't find one elsewhere.
Short action:
SA Matte part number 107605 for bottom bolt release
SA Matte part number 106238 for top release

Long action:
LA Matte part number 105857 for top bolt release
LA Matte part number 106706 for bottom bolt release

Hope this helps. IMHO if you are using the rifle primarily for hunting, and your local laws are like they are here, sticking with the factory DBM set up not only eliminates that pesky 5-round max rule but also gives the bottom a more sleek/slim profile (no extra magazine sticking out).