I'm not sure what area you are in, but in the Southern California area the current public price per GGE is running in the $3.00+ range on average. The Phill unit from Fuelmaker is about $4,000.00 + installation costs which are in the $1,500.00 - $2,000.00 area. Based on the rate per KW and a discounted per therm rate from the gas company it works out to about $1.25 per GGE. Phill's output is 0.4 GGE, or about 2.5 hours per GGE. To be leagal in California a conversion must meet CARB approval. There are several shops that can do that work. Installing a conversion system is not something that is a DIY project. High pressure gas systems take special training and compliance with all applicable codes and regulations.
Besides the Honda Civic Gx you can get Ford products via BAF Technologies in Dallas, TX. depending on where you are located you may be able to purchase through your local Ford dealer.