Was shopping around for parts to complete the can cannon upper. This was the best deal I could find for a BCG:
https://www.armorally.com/shop/toolcraft_5-56_nato_black_nitride_bolt_carrier_group/I've seen good reviews of Toolcraft. No frills but does the job.
The bolt itself is 9310 steel, for $10 more you can get Carpenter 158 steel. From what I have read the Carpenter steel is mil spec but the 9310 is a better.
http://faxonfirearms.com/blog/tag/Carpenter+158