Well, I finally did get an brand new OEM Pentax LCD window for my K-50. I have not installed it yet, but when I do I will comment here about the process. I am waiting until I have the time and patience to do it right.
Originally I bought the K5/K7 window not being able to find the K-50 window anywhere! It will fit the K-50, but the appearance isn't exactly the same. I did not install it as I was determined to find a source for the exact part.
Although Pentax can no longer sell directly to individuals, they were very kind to email me part diagrams/lists so that I could get the exact part number.
I decided to ask the seller of the K5/K7 LCD window if they might be able to obtain the exact part for the K-50. I was advised they likely could and would get back to me. Email with the seller was scant and very limited to the extent it gave me no confidence they would get one. Assuming they would get one eventually, I did not want to change the condition of the one I bought from them so that I might request to return it for a refund less shipping of course. It seems that after I mentioned that was my intention in email, all requests for updates on the status of the K-50 window ceased. Making sure I kept within the 14 day return policy of the eBay auction, I requested to return it. I was met with a stern admonition that the LCD window will not fit and that I should not have ordered the wrong part. eBay was of no help in this situation. Not wanting to waste my time with them any longer I started asking other sellers of parts for Pentax cameras on eBay if they could get me one. Two sellers offered to attempt to get the part.
There are a lot more details about the exchange with the first seller which turned out to not be very customer oriented, but including all that here would be excessive and mostly boring, but this one really stands out. "we put this in the ebay add specifically to address this issue. did you read this...................."
Regardless, reading all of it I think would give anyone a bad impression of that seller who sells the K5 window with tape for $41.20 free shipping on eBay (when I bought it, it was $45.20) and also now lists the K-50 window on their internet site apart from eBay for $36 plus shipping, apparently now that they have gotten them in stock. They never bothered to advise me they received them for sale, and I stopped asking for updates after I realized what was happening.
One of the other sellers (parts-trader-llc) did come through for me. His communications were very polite and he always followed up with me about the status. Yesterday I received from him a brand new LCD window with the pre-cut tape for $20 including shipping. I feel like I can depend on this seller to provide parts at a fair price in the future. I will certainly look to parts-trader-llc in the future for any Pentax parts needs before checking anywhere else.