What you need to get is the drive shaft and drivers out of a 05 440 sno pro race sled. You'll also need the chaincase side bearing as well, I believe your bearing size is for a 1" shaft and the 440's is a 1 1/16". Check on ebay you'll see them there from time to time.
I'm not positive that one will work because its for a 06-07 sled? I've done what your doing before and I used the one out of a 2005 and with the 440 chaincase side bearing it will work. Looking at the parts diagram below they look alike but the speedo side looks sorter on the 2006? So you might have to have a 2005 440 one only (not positive)? I'd hate to tell you to buy it and not have it work.
Almost forgot that the chaincase side where you bottom gear goes on is different as well. It takes a 16 splined gear rather than the 15 splined thats on there (something like that) You'll have to look at them when you get it. Basically all you'll need is a different lower gear.