Many feed stores will do special orders. If they do, I would suggest getting either black or red sex-linked chicks. They can be sexed by color and therefore no mistakes. Otherwise I would try and find someone with started pullets. What area are you in? I know a few people in my area that have started Buff Orpingtons and RIR's. Some are easier to tell apart than others but you can get a pretty good idea by about 10 weeks if they are male of female. To be positive you have to wait for hackle & saddle feathers or eggs and that can take as long as 20+ weeks.
I had 5 Large Breed Hens (Brahma & BO) and a Drake in there this last winter (and this very chilly spring) and they all did fine. They stay outside most days regardless of weather. I didn't add any heat just plugged in an electric dog dish so I didn't have to haul water. I live by armour & wagner So it is a little bit warmer but pretty similar. We also have a cat who takes care of our mice but once they are in the insulation they are tough to get rid of....so In my opinion insulation is not necessary that is what their feathers are for. Just make sure you have enough ventilation so it doesn't get humid in the winter.
