There are many different styles of stainless sinks, single bowl, double bowl, top mount, under-counter mount, offset bowl, offset elongated bowl, and the list goes on and on. The typical RV size is 25x19x7".
Here is one possible selection from Trekwood. Their pricing seems high and you may find much better prices at Lowe's or Home Depot if they will special order the correct size for you.
http://www.trekwood.com/products/498...ainless-Finish