Does he have the old can or is is broken or missing all together? There are a few Snowmobile wreckers that have acres of old sled so that might be the only way to find a good one.
My Dad had a 1960 with wooden ski's and I drove it when I was 11. The first Skidoo I owned was a 1969 Olympic 335, What I wouldn't do to have those 2 sleds now.