What you want is called a 'concession trailer'. There are manufacturers who specialize in these and can give you a better unit, cheaper, than Airstream.
There are also used units available in all price ranges.
Here is one company, picked at random from the internet.
I am not sure if this will help, however, in Pensacola Fl there is a Airstream Food Concession Park. It consist of about 6 vintage AS that were converted so they could serve food. I believe they are permanent. I enclosed to pictures
I failed to the load the pictures the first time this should work. Anyway you might want to look them up on the web and contact them to see who did the work.
Timeless Travel Trailer (Wheat Ridge, CO near Denver) specializes in these kind of conversions. They are not cheap, but they are really good at it. Their web site is at http://timelesstraveltrailers.com/.
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