NH northern tools has quite a good selection for New Diesel engines:
Diesel Engines | Engines | Northern Tool + Equipment
I'd go for the Kohler Diesel Engine — 401cc, 1in. x 3.62in. Shaft, Model#KD400
It goes for Only
$1,899.99
KEY SPECS
Displacement (cc) 401
HP 9.8
Torque (ft./lbs.) 16.6
Engine Type
4 Stroke single cylinder
Shaft Dimensions Diameter x L (in.)
1 x 3.62
Shaft Keyway (in.) 3/4
Manufacturer Warranty
3 year limited warranty
Ship Weight 110.0 lbs
Item#60277
It would jack the project price up a bit but it's really what you're looking for.
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