You can visit your local appliance dealer and get some appliance boxes.
All you need is the FFL dealers number and you can look them up on the A T F EzCheck website. You don't need any actual paper copy (this apparent requirement stems from 'the olden days' before the internet).
Under Federal law, you are only legally required to ship to an FFL if doing an out of state transaction. You do not have to have any kind of copy of the FFL license in hand. I'd really suggest you utilize the EzCheck system, though.
The EzCheck doesn't work for C&R (ffl03) license holders, so for this, a signed copy is needed.