I hate to contradict you, but dual-layer DVD players are standard everywhere, and as far as I know, always have been. Even the cheapest players you can buy. I'm pretty certain that it would be more expensive for manufacturers to build and stock two variants, than to have a single standard.

I believe that the issue of single and dual-layer drives only arose with the advent of the DVD burner, and even single-layer burners function as dual-layer ROM drives. Perhaps your issue is something else. There are double-sided, as opposed to dual-layer discs. Could that be what we're talking about?

There is a simple way to verify whether you can play dual-layer discs. Take some commercial DVD's that do work in your player, place them in your PC's drive, go to "My Computer", and right-click the disc to get the properties of the DVD. If the used space value on any of those discs is over 4.4GB, then they are dual-layer.