Dont forget the little mitten wool balls for your testicles to sit in! You could use a woolly hat and sorta fold it in half for this purpose. Also Ipod and headphones
Hot water bottle a must and several. Warm gloves and possibly if you can then purchase an oil lamp or similar. You NEED to keep warm and have shelter. I dont know how cold it gets where you are but if its say for example like Alaska then you MUST have good warmth and that tent be sturdy to shelter you.
Perhaps have some snacks around to keep your energy up and moral boost depending on how long you sit in this thing for stretching and tugging away
Any chance some nosy fucker could come out pull the zipper down and see you bollock naked? if so then have an explanation ready! i.e ''I saw a dark shadowy thing that looked like a spider creeping around the place and it shot into this so I investigated. Turned out it was one of those nasty tarantula things that likes nothing better to dig its fangs into mens willys! It shot right up my trouser legs and I had to whip me pants off and beat it away, so that is why all this crap is all over the place and am naked in here!''
It was the Willy-Tarantula and they live all around here, like to come out in the Winter because they seek shelter in warm houses.