Hi, Yukon Resident ringing in on this one.
1- Animal knowledge and common sense are your best defence against bears and wildlife encounters, bear bangers. bear spray are also helpful. Take a "Bear Aware" course to learn proper techniques for travelling in bear country. Portable electric fences or warning fences can add to the peace of mind.
2-Firearms and ammo must be declared and the proper importation paperwork must be filled out when you pass through customs. Use or possession of a firearm illegally in Canada is a serious offence and can result in criminal charges, seizure of your weapons, deportation, jail time, and a ban on entering the country in the future. Best leave the guns at home, this isn't a video game or action movie.
3-If you're worried enough to ask about a "Bear-proof" camper, maybe consider a more gradual progression to your introduction to wilderness. Adventures guided by knowledge, respect and caution, result and skill development and growth. Trips steered by conjecture and paranoia often have disastrous results.
If you have any questions about travel throughout the Yukon, NWT, or Alaska, message me your questions and I will provide whatever advice/ knowledge I can.