The part number is 128170-76790, I suppose a Yanmar dealer could order
you one. I got one with each of my 2gm20f engines, so I figure they
should be workable, but I have not tried. I have hand cranked a 1gm
and it was a two person job (one to crank and one to work the
decompression levers) and was no fun at all...

-- Tom.