If the court has reviewed the matter and found that no child support is due, then there's no legal obligation to provide anything to the other parent -- that each parent is responsible for the support of the child when that parent has custody. That would seem to transform the text message into a promise to make a gift -- and you cannot sue to enforce a promise to make a gift.
If you're caring for your child, and your child wears diapers, it's nobody's fault but your own if you choose not to buy any diapers or wipes before the child visits. The remedy is to make a store run; the same is true of baby shampoo or whatever other toiletries you have failed to purchase for your own use. Similarly, there's no law that says you must provide the other parent with a full wardrobe for the child during visits -- some parents have a real problem with clothes not coming back after visits, or coming back ruined. You're free to buy some clothes to keep at your home -- if you don't want to pay retail, hit resale shops, thrift stores or goodwill, which generally have a lot of baby and infant clothes -- and to return the child in the (clean or laundered) clothes they wore when they came over at the start of your visit.

