Any small low container with about 1 inch sides will do. The chicks will stand in the food to eat anyway. You can buy chick feeders from the same place you buy your feed from.
It can get moldy if it's left out too long. Just like anything else that has wetness (such as clothing left in the laundry machine too long.) I think it'd probably be okay to sit out for a day with...
Vitamin D is available in many Tonics you can buy from the feed stores. This tonic is often administered in a water soluble form and put directly into the chicks water supply. Good chick starter feed...