John,
A bargian is a bargian, but in this case I'm going to suggest its not a very good idea for the environment your headed into.

Reasoning:
First suction cups fail and you could end up in the back country with out a compass. Bad thing!

Second, THere is big water in the BWCA when the wind picks up. A good slap of water and your compass would be off the deck and you'd be chasing a black object in dark water as the wind and waves are hammering your boat. Bye bye compass

Three, The compass in your picture doesn't have a very accurate way to take bearings. Often portages diverge of the same path to different lakes the easiest way to make sure your about to take off on the right lake is to get an orientation down the lake and compare it to your map.

Four: John the biggest use of a compass in the BWCA is to orient the map while your comparing it to what is around you. Cheap compasses are often very inaccurate. Turn a map 10 degrees in an unfamilar setting and often things look either right on target or look like your lost. Either way its disorienting, and that leads to getting lost.

John, I know you go off on tangents and I respect that as one who is often tangential, but trust me on this one. This is about safety and on a solo safety choices are critically important. John it is essential for a person who is going solo in the BWCA to have a good non electronic means to orient themselves. Its worth spending good money on a good compass.

Wall mart also sells several good marine compasses for a few bucks more. You might have to adapt the fitting, but its worth it.

Most importantly, You don't necessarily need a deck compass to do the BWCA. Its nice on big lake crossings, to keep you on a specific bearing, thus shortening your trip. But it is still essential to have a good compass even if its not on the deck.

When I do the BWCA I carry a pocket compass on a lanyard tied to my fishing vest, that holds a ton of other stuff. My pocket compasses, works on water and when I am scouting portages or just rummaging about in the bush. I have a host of them. But they are good ones. Brunton, Silva and Sunto are all good brand names. Each has a mirror for signaling and orienting straight lines.
They also have very exact bearing markings. Rember 3 degrees off the mark is a long way off at distance. A cheap compass can be way off and a few degrees in the BWCA can be the difference between the lost and the found.

John pleas!!!! play this one safe. Plunk this one on your car dash board. Then Spend some good money on a compass worth staking your life on. Remember, after your life jacket. Your compass is the most important piece of equipment in the BWCA.

If worse comes to worse send me an address I'll loan ya one of mine!

!RUSS