Ordering bags or buying bags direct from a bank is handled just like anything else. Just scoot on up to the teller line, ask for the vault teller, and inquire to buy a bag or order. That's the best way to find out, or to get shot down. It's easier if you are a regular customer, and have been with that bank for awhile, although not always necessary.
A few banks that I deal with take in excessive amounts of coin from customers, and I intercept those bags before they are shipped out.