Digital Nitrous gage, where to find????

[OIF1VET]

I am looking for a digital nitrous pressure gage that also shows how much spray is left in the bottle.. Saw one in a vette a couple years ago.. Did some looking but all I can find are strictly pressure gages, similar to this:http://www.glowshiftdirect.com/elite...ure-Gauge.aspx

[1BADAIR]

http://www.trickperformanceproducts.com/tpp_00029.htm

[OIF1VET]

http://www.trickperformanceproducts.com/tpp_00029.htm

Can't find a price, but guessing it's more than I want to spend...

[squareandcompass]

http://www.glowshiftdirect.com/blue-...ure-gauge.aspx

edit: Well shoot. Looks like this isn't the gauge you'd want Larry, as this gauge doesn't show how much bug juice you have left after each use. Sorry - just trying to help.