I did some searching and I didn't find anything online that fit your description.
Have you seen one that fits your needs? Maybe a picture of it?
I usually find something that I like and draw up some plans and add my own little touch to it. But it does take some time to do that.
But I have never found any plans that I could use to build my projects.
Most of the plans I find are lame...
How large of a ledge is she wanting at the top? And are you just wanting beadboard (1/4") for the back portion?
I will continue to search and see what I can find, but if you have a picture of what your after that would help.