Most of the time when I've had to work on an air-gapped network, I was also provided with a second computer connected to the Internet. I found that to be a good compromise, though getting small code snippets or scripts onto the air-gapped network was a pain since I had to type the whole thing or bug IT to transfer it.

I say most of the time, since I once had to work in a very high-security environment with no Internet-connected computers in the area. I had to leave the secure area to look up things on my phone. It was a nightmare.