I hunted the Yukon in 2016 and had an amazing hunt. It was with a smaller outfitter (Reynolds Outfitting with only 4 moose hunters per year) so he gets booked out years in advance.
I would highly recommend Bonnet Plume Outfitters. They take some amazing bulls every year and have an operation set up for a variety of access methods. Also, I would'nt rule out some of the NWT outfitters as well. Canol Outfitters, Mckenzie Mountain Outfitters, and Nahanni Butte Outfitters all take some great bulls and with it being in the NWT, retrieval can be easier with the use of heli's.
Just my 2 cents. Good luck, I wish I was planning another moose hunt up there!
Glen