gun shop, gun show, pawn shop, want ad.
Try e-gunparts.com or MidWest Gun Works.
Check the receiver, barrel, under the forearm
Try MidWest Gun Works
Contact Browning.
Try Calbelas Shooting Catalog, that's where I got my stock and forarm for my auto 5 light twelve. Why they named it the light 12 is beyond me.
Check Browning's website.
usually the stock is behind and the forearm is in front of the receiver.
Try MidWest Gun works or egunparts
Try Mid West Gun Works.
You can find them on eBay periodically and at Gunbroker.com. also Midwest at the related link listed below.
Try e-gunparts.com
Browning, gun shop, gun show