Water Heater for Food Truck?

Hello.  I'm just about finished with the build out on my truck, but haven't found an ideal solution for the water heater.  I purchased one months ago thinking it was perfect, only to find out that the type of air intake and venting (atmospheric) wouldn't work for this application.  My sinks are relatively small, so based on health dept code I should be fine with 2.5 to 3 gpm tankless or 15-20 gallon tank.
 
So, what type/brand/size of water heater are you using?
 
Thanks, Angela