You may be able to achieve this by taking off the butt plate/recoil pad and then access the bolt that keeps the stock tight by a hole through the wood.Use a penlight tom see what type of bolt nut,or screw slot is there before you tighten.
In front of the butt stock .
The butt of a rifle or shotgun- the part that goes against your shoulder.
Mossberg 500.
I have one for sale. Message me @ garym6@cox.net
Remove buttplate. Use a socket extension and rachet to unscrew the stock bolt (it's in that hole in the center of the butt)
There are two small holes in the butt pad of the stock. Lubricate a Phillips head screwdriver into the holes and remove the butt pad. Using a long flathead screwdriver remove the screw in the center of the stock. To add new stock simply reverse.
I have one for sell in very good condition.
The butt plate screws (2) at the end of the stock must first be removed. You will need a long shank flat tip screwdriver to remove the screw at the bottom of the center hole in the stock butt. Reverse to reassemble.
Remove the butt plate. There will be a hole. There should be a slotted screw at the bottom of the hole. Use a long screwdriver and be careful to not damage the stock.
You will need to provide a DETAILED descripton of ALL markings, gauge, barrel length, forearm, butt stock, etc..
Try e-gunparts.com, gun show, gun shop, want ad.
LONG out of production, the company is no more. You may find a used stock at gunpartscorp, but you would need a match to the correct model- there were dozens.