There is no uniform rule for the number of menu items for a food trailer and should be determined based on your food trailer space, number of employees, customer base, etc.
You can use Google and B2B platforms to find ice cream cart manufacturers. You can find a lot of manufacturers in Google results and B2B platforms, but you also need to find good ones.
Ice cream trucks, ice cream trailers, ice cream carts and ice cream bikes each have different advantages and disadvantages, and you need to choose the right one according to your needs.