Try e-gunparts.com, gun shows
Browning does not make an A bolt shotgun, they sell an A bolty rifle
Try on line gun stock sites, gun shows, gun shops, egunparts and Shotgun News.
Belgium
Last year I bought a Browning A-bolt 22 rifle for 300 dollars.It was new in the box.
For a new in the box Browning A-bolt II medallion,the price is 805 dollars in the caliber .270Win short Mag.
Used 600-700 New 900
Japan
like new 850 poor 200
I just paid 300 dollars for a new in the box browning A-bolt .22cal rifle,that was made in 1989.I feel that mine is priceless and will never sell it.
Recommend seeing a gunsmith
first get you new stock the take the butt pad off of both the new stock and the old there is a bolt inside thread it out and put the new stock on and put the bolt back on then replace the butt pad
650 USD