Where to go depends on how much you are willing to spend. Newfoundland is a good value. Lots of moose but not a lot of big bulls. Expect bulls to run 30-40" with a few bigger. Cost is between $4000-$5000 a person. The farther west and north you go the price goes up. The middle of Alberta runs 5-$6000. Northern Alberta and B.C. run about 8-$12,000. Alaska,NWT and the Yukon run between $10,000-$20,000.
If your just looking for the moose hunting experience and don't have to get a bull consider putting in for a cow tag in the lotteries. Non-residents have decent odds on cow tags, especially out west.