Special Jr. Groomsman Gift

Need ideas! My step son, who is turning 6 just before our wedding, is going to be a Jr. Groomsman in our wedding. We are already married (covid bride), and he was not present for our initial ceremony (they live far away with their mom), but very much want to include him and his sister in our big day this June! I have the cutest things for his sister as a Jr. Bridesmaid gift, but I’m stuck on what to get him, and my husband is as well because he’s so young. Would love to get him something he will have forever, but I am racking my brain on what that could be for a 6 year old. They are going to be included in our sand ceremony on the beach and he is very excited about that. Any ideas, I would love to hear them! Gracias!