your best bet would be to email LE with the question. Their support guys have been a great help to me. lincolnelectric.com
A local shop might help also, but I haven't had much luck with locals. It seems "the guy I need to talk to" is always out and the other people in the shop seem as knowledgable as me(I'm VERY new to welding).
If you do find out the part # needed let me know.
thanks.
the new miller passport has a paintball co2 tank installed in the actual machine. The Miller part number for the regulator is 218950. I would suggest that you see your local supplier and get some pricing on this unit. it is a regulator/flowgauge that is designed to fit these bottles.
the only drawback that I can see in using the paintball tanks, (unless of course you get them for free) is that with a 12 ounce bottle, you will get about 25 minutes of trigger time.
At any rate, you could check them out.