Well, if you dig around a little, you will find that a lot of brands share the same screens, so if best buy or fry's or whatever doesn't have that exact model, you may be able to find a different model that has the same screen.
IPS and PVA screens are way more expensive, but nobody wants 4:3 screens anymore, so I got my 21.3 inch NEC for 150 bucks, and its flawless. The screen is 17 or sinches wide by 13 or so inches tall, its plenty big for the cab I am putting it in. Yeah, I know there is the whole thing about getting used LED screens and having them wear out,etc, etc. But this is a 600+ dollar monitor brand new, its rate to 30,000 hours or so, and its not like I am going to be keeping my cab on 24/7 so 150 bucks is worth it to me.
what are the interior dimensions of your cab? I would consider getting a 21.3 inch pva or Ips screen. Most all of the 21.3 inch, 4:3 ones you will find will be PVA or IPS.
Other than that, like I said, I don't think viewing angle will be that huge of an issue with just two players, and most TN screens have good horizontal viewing angles, but not very good vertical ones, so if you are going to do a traditional horizontal mount, I don't think it will be much of an issue.