So I had a thought.. Rear shock nitrogen charging solutions

I don’t see why not. You’d have to set up a regulator and hose type connection.

This is what I got for my tank. Was a bit larger than yours, but less pressure, and you'd have to make sure the connections are compatible. Works very well.

http://www.ebay.ca/itm/162156887160?euid=2c6e15346d30441fb028f0095f7b7b…

You'll need some place to fill the tank with nitrogen. Many places will not fill a tank that is not intended for the purpose, etc. It might be just as easy to pay the deposit and get the tank from the gas place. I bought my own tank about 20 years ago. It's a 65cf tank, comes up a few inches above your knee. I've probably filled over 100 shocks with it and it still has over 7,000psi in it. Pretty sure it will last the rest of my life.

Honestly nitrogen is freely available. Pump air via a hi pressure bicycle pump or one of those air fork pumps is sufficiently dry. Giving nitrogen a grade of A the pump air would be an A-.

Those aren't really nitrogen tanks, they're hpa. High Pressure Air. Aka normal air, which is mostly nitrogen...
You can play paintball and get it filled for free right before you leave. I usually top my tank off before leaving the field. Good to have air at home for working on the guns.

Also the tanks have a regulator on them. Ninja and some others sell their tanks with adjustable regulators. Not sure what the lowest limit would be though

Look to the aviation field. My dad has a small tank for his planes and we use it for shock rebuilds when needed.