Anian clothing in BC is another option. 80/20 wool blend. Wait for a sale and some good deals can be had. They have tall sizes. Fyi...wish they made their sleeves alittle roomier for layering....do consider that. I did hear they may be planning to do that as others haved noted the their sleeve taper could be a tad looser for layering when needed.
Filson also seem to have narrow taper sleeves on some garments.
80% wool is regarded to be a good mix of thermal ability and 20% other for strength and shrinkage control. May be worth considering.
100% wool is hard to come by. Maybe find some wool blankets locally and get someone to sew something up if you really are set on 100% wool?