Pic of missing window

That's gonna be a tough one. I think OEM is going to be the only way to go.
You can post the model name and year to see if anyone is parting out the same boat.
Price wont be cheap but at least you can put it in yourself.
 
YES! Unfortunately, it is not being made anymore. Custom glass out of Florida at around $5,000. ANYON̈E PARTING OUT A 300 MARLIN??? If I can't find one, I'll likely have it made in acryĺlc have a jaì