Just pick up an assortment pack of these little plastic retaining clips and after lining everything up the best you can, simply press one into the hole where the old one was. Also it would probably be a good idea to check the other clips around the one that’s missing and make sure they’re not loose. If so just pop them out and put in new ones. Keep in mind that there are literally thousands of these little clips all over your Scooby so having a set of these on hand will safe you a few headaches down the road.