We have updated the interface for store and add-on items to be much easier to use and nicer to look at! At the right is an example of what an item would look like on a phone.
Below are some other examples. One recommendation is to put an image (or not) for each item so they align properly.
Mobile View of a Store Item with custom colorsExample of a Free Add-On with Limited Availability and Deadline DateAdd-On Items displayed during registration