Sun X = Factory Tint option
You'll be hard pressed to find a matching aftermarket "film" tint that closely matches.
I'm fairly certain that a factory tint car would get you "all" glass tinted, but I'm not 100% on the windshield.
If you mistakenly bought/have a piece of Sun X glass, suck it up and find a piece of non-Sun X glass to match the rest of the car.
You're right, eBay sellers often do not stipulate/are not aware of the difference between a regular piece of glass and a Sun X tinted piece.
Fortunately for you, there's probably a guy somewhere with the exact opposite problem as you.... all of his glass is factory tinted except for his drivers door glass and he's pretty much in the same boat as you. Ebay has lots of glass listings, add yours to the list and then find the right piece for you.