A friend of mine has a Marlin 20 ga. bolt action shotgun, not sure of the model number. He is looking for a replacement magazine. Can anyone help or give direction to where one might be available?

There are a few companies manufacturing magazines for obsolete firearms. You could try any one of these:

http://www.wisnersinc.com/

http://www.brownells.com/

http://www.sportsmansguide.com/

Wisner's is your best bet of these three.

Hope this helps.

Appreciate it. I will forward to my friend with the gun.