Any "Big Box" Home Improvement store might have what you're looking for. It won't be found in any RV store. A sink to do what you want does not have to be RV specific. Just to minimize some cutting, but you have to know there won't be an exact fit, make sure to accurately measure the sink opening you have today............then measure again.
Like they say........measure twice, cut once.
Ken and Terry
2010 Georgetown 330TS being pushed by our
2017 GMC Terrain toad (4 wheels down)