Get Gorilla Glue, you can find it anywhere. Get a piece of fabric like a T-shirt. Cut it into small squares. Deflate the air mattress in this process and know where your pinhole is! Put Gorilla Glue on the felt and then on the fabric. Push it on to the hole. Then get a hair dryer, keep a little far away on warm for 2 minutes. Let it dry 3 to 4 hours. Fill your bed up and it's done.
Hope I helped someone, good luck!
This page is about finding leaks in an air mattress. It can be challenge to determine where the holes are, when an air mattress deflates itself.
This is a page about finding replacement caps for your air mattress. An air mattress without its valve cap is not very useful.