Their was an outfit at Oshkosh called I think Delta Hawk or similar - I know they have a web site somewhere.
Better known is Zoche in Munich which you can see at
www.zoche.de/diesels.htm
Historical note - there were many diesels in the 1920s - 30s - Maybach, Daimler-Benz for example. And Junkers had one engine used in many transatlantic airliners - a 2-stroke diesel capable of operating up to 50,000 feet in reconnaissance planes.
HTH
Diesel