Has one built in. When I first started nitro assisting and spoke with @FarmerJoeParker about it, he’s the one that put me on that path. He was suggesting that I disassemble one and use the membrane when vac’ing out nitro, to be completely safe.
https://www.ebay.com/itm/Peak-Scientific-NM30L-Nitrogen-Generator-/273563858758
For a description of its capabilities