Shopkeeper's Mobile Shop

From time to time, usually once per year in each town and village, a strange dark red wagon rolls into town, stops in a flat part of town, and then sets up shop. What really happens is that the driver unhooks the horses, says something to the wagon, and wagon changes shape into a buiding that fits the style and size of what would fit for a shop. In small villages, this is often a building larger than any of the cottages, while in a major city, the wagon changes into a normal two story building.
After a few days, the Shopkeeper, says a few words to the store, and it changes back to a wagon. He hooks up his team of horses and moves on to the next town.
It's what the shopkeeper sells that is always of the most interest to the populace, for the shopkeeper tends to sell a bit of everything, especially if you have the coin.
When you first enter the shop, the room is common and holds everything you would find in a well stocked general store. There are food stuffs from around the world, but never fresh produce, unless he traded locally for it. Utility goods such as ropes and shovels, tack and nails, tools and lanterns are plentiful. Bolts of common cloth can be found along with the dies to change the color. Even common weapons and armor are available. The contents of the store always fit the market. In a village, the main room has what the villagers need: tools, rope, plows, and food. In larger cities, the bolts of cloth might include silks and high quality weavings.
However if you need something that is not on the shelves, the Shopkeeper might go to the back room for a brief time and return with the item.
Should a person find themselves in the backroom, it is completely empty except for a bed, dresser, and table and chairs, and the shopkeeper will never be found in this room if he has gone to retrieve a special item. He simply disappears after going behind the curtain.
He is usually unwilling to haggle, but his prices are always fair for the area. He will discount prices to the poor, and has even been known to give stuff away.
But the shopkeeper has one thing that everyone can get for free when they visit, a small homemade ice cream cone. Most people in the world have no idea what ice cream is, and as such people line up to get one when he starts serving it during the heat of the day.