Perhaps a Raised Panel Cutting Bit could be used to make such a profile. There are several different shapes to choose from at "Lee Valley Tools". I suggest you use a cutter in a table mount router! For safety, you should consider using a cutter with a 1/2" shank!
Search - Lee Valley Tools <> OR Try <> Woodworking Router Bit 1/2 inch Shank T Shape Wood Milling Bit Tongue and Groove Tool Sets Raised Panel Router Bit Woodworking Milling Cutter for Grooving Different Depth Notches : Amazon.ca: Tools & Home
Improvement You will change the finished product profile dimensions by raising or lowering the cutting bit at table top. Hope this might help you find a solution. Best of routing fun! Please remember Safety First.