By all means get a spare.
We are also headed to Alaska and are carrying 3 spares.
I had a flat last week in Livingston, Montana, and used my Trailer-Aid. As stated, it will almost do the job. I used a 2 1/2 ton floor jack(Harbor Freight) to lift the axle of the flat enough to put on the spare. I carry a 4 way lug wrench, the Trailer-Aid, an 8 ton bottle jack, the floor jack, 2 axle stands for safety, half a dozen 2x6's 18" long and my torque wrench with a thin socket that fits my lug nuts.
It took me 30 minutes to change the tire and be back on the road. Road service could have been hours.
I was lucky to have pulled off at the exit for fuel and noticed the tire missing a 16" piece of tread. My TST 507 Tire Pressure Monitor System will be here tomorrow.
It did very little damage to the TT and still had air in the tire at the pump. It was flat by the time I filled and moved from the pump.
You WILL need a spare......or several on this trip!
Get a spare and practice changing it on flat ground. Things will be considerable different on the side of the road.
2001 Ford F-350 Super Duty CC Dually, 7.3 Diesel
2013 832IKBS Flagstaff Classic Ultra Lite, Hensley Arrow Hitch, Carlisle tires
2016 days camped....211, it ain't over yet!
On the road to ALASKA May 6, home Sept. 13, 2016. 23 states, 3 Canadian Provinces, up to the Arctic Circle, 17,300 miles, 131 days on the road. 1 flat tire, 4 oil changes. What a beautiful trip!