I am looking to have a pump shotgun refinished.  
I am looking to maybe have it Parkerized.
I do not know where to take it to get a good, but reasonable job done.
I am not looking to pay more than a new shotgun would cost me.

IMHO.  Sell yours and buy a Remington 870 express or Mossberg military model.  Remington is kind of parkerized.  Unless you have too keep the shotgun you have

I had ADCO refinish my 870, it turned out very nice.  

https://www.adcofirearms.com/shopservices/shop_qnew2016.cfm?code=Finishes

Thanks for the reply guys....
Actually this shotgun is a Rem 870 home defense shotgun. Always clean it and oil it and keep it inside, never been out in wet weather, but rusting and has been rusting.

One of the easiest guns I have ever had to get rust on it. I do not keep it in my safe as it sits by my wifes side of the bed. I have a Mossberg 500 on mine. The Mossberg is probably 20 years older than the Remington, no rust on it.

It is puzzling, but I like the gun, just not enough to put more into it than it is worth.