If the gun were mine, and if the barrels have decent wall thickness and are not to badly pitted, I would search for another parker of the same type and of the same era with a stock in better shape. When looking, bring the barrels with you, and ask if you could check to see if your current barrels would fit the prospective new purchase. If so, you may be able to come up with a two barrel set without having to put much money into your current gun.
Many barrels will not fit perfectly but with some gunsmithing adjustments you may get lucky. You may want to ask someone like Brian Dudley about the possibility, and cost, of having this done. Good luck and good shooting.

The gun is looking very nice..How much you paid for it?