There are some based on Chevy Brightdrops. Here's one that is based in Tacoma:
This one is even closer; I met him at a local gathering and got some great ice cream. It's the one on the left; he was still finishing the conversion and hadn't put his marketing wrap on yet. (My van is just to the right of his. The dark one further on is a plumber, and the last one on the right is a van being DIY converted to a camper).
This one is from Norwich CT:
Someone converted this one, then put it up for sale before deploying it:
On the Brightdrop forums, there are several other members that are in the process of converting vans to ice cream trucks, or are looking for a van to convert. Of course there's plenty of food trucks too.