I know this post is really old, but I recently started looking for a source of beer gas too. I thought I'd share, since others might come across this thread later. Parkit Market in Dallas sells and swaps out beer gas cylinders, but they were out when I went, so I suggest you call them before you head there. I ended up buying a new 20 CF nitrogen cylinder online (about the size of a 5 lb CO2 tank) and was able to get it filled with beer gas at Red Ball Oxygen in Grand Prairie. It only cost me $8.19 plus tax (for the gas only), but I had to leave the cylinder with them for a couple of days. I wasn't able to find anyone further north in the area who would sell or fill cylinders with the 25% CO2 / 75% N2 beer gas mix.