I have one of them in our Bus. It has one large file drawer on the bottom and one smaller desk-type drawer on top. There are guys at Red Bay who do custom work. Chris Berry does most anything in woodworking that you might want. He works in the cabinet shop but does side work evenings. Check out
http://www.rvtechlibrary.com/redbay/afterhours.pdf in the RV Tech Library for contact info on all "after-hours" techs.
I've also seen some nice desks at Bradd and Hall. See
Bradd and Hall RV Furniture for examples but they can make anything. The advantage of Chris Berry is that he can most likely match your existing solid surface countertops.