We booked with Temsco, got their phone # from their Web site. Dog Sled was $40pp less than through the ship, but, know that you may not use the cruise transportation from the dock to Temsco, either the city bus or a nice 15 minute walk.
Also, they require $50pp depsit in advance & the balance paid the day of tour in cash, check, travelers checks, they do not take credit cards.