Blimey! That's a lot of kit! Do you know if any of it can be rented when there??
Actually it is not a lot. Most of it you may already have, or can use as regular bushcraft or winter wear (i.e. wool pants, sweeters, scarf, knitted cap, etc). The special kit (warm parka, thick hat) is a bit special, but one could find stuff second hand or surplus, or make do with a bvery thick knitted cap. The swedish army m90 parka is excellent, and only cost me SEK 195 surplus... Even an old fur coat sized very large (it must fit over all your other clothes) would do, as would other things. Yes, I could check the surplus places for the M90 parka and make a group buy and distribute in connection to the course.
I'll post a pattern for mittens later; it is dead easy to make from some canvas, suede or soft leather and a piece of wool blanket.
Sleeping bag; use your summer and "winter" bag (-15 C or so) inside each other, and you will be fine. Synthetic fill is actually preferable to down, since damp is not as major a disaster (I've seen everything from +2 C and sleet to -50 C and hard winds, but you won't be allowed out in the latter)
The big one you can't excape is boots. My only suggestion there is to bite the bullet and spend some cash. The Nokian boot is fairly cheap (about SEK 1000 IIRC); you can easilly spend twice that and get less performance. See it as an investment; the next time there is a snow storm and everyone else waiting for the bus is freezing their toes off yours are toasty. The wellie type is good, since you will not get wet even in warm temps, and don't have to battle bootlaces in the cold. Mine are 10 years old, and a bit tight since my feet has grown a size since then, but other than that in fine shape. Bring plenty of socks and try size "how big did you say!?!" in your regular stores.
Basically; look at what you own, see how many layers you can make up from it (even adding big baggy sweaters from Goodwill is an option instrad of the parka). And long johns under regular army pants will do, even if it will be a poorer choice if the weather turns bad. The Helly Hansen fleece pants aren't bad if you want to add insulation (when I did my military service up north over two decades ago I wore a pair of those under the grey wool pants, and was quite comfy in -40 C).
My bet is that you have -- or can justify -- most of the kit, or can bodge up substitutes for the price of feeding the familly at McDonalds.