Powertank makes a really nice nitro setup with the no loss valve. I bought a kit from polyperformance when I started building my buggy. It wasn't cheap but I just got tired getting bent over at the motorcycle shops to get shocks charged.
http://www.polyperformance.com/shop/N2-Race-Shock-Inflator-Kit-p-16519.html
http://www.polyperformance.com/shop/N2-Race-Shock-Inflator-Kit-p-16519.html