Not sure about status of deltahawk without checking website:
DeltaHawk Diesel Engines
Another very competant design to watch is the Wilsch AirMotive (also a 2 stroke design):
wilksch.net
One development that really caught my eye a while back was Cubewano Diesel rotary:
Cubewano
These last guys are a clever spin-off from the Norton/UAV rotary with a clever combustor design to handle either diesel or kerosine. Designs large enough for private helicopters are on hold pending DOD funding, which is a great pity IMHO.
Or you could fit a Perkins and sacrifice a little payload...
Perkins