As you said that he is young at heart and is 41 years old..so what else except a wonderful beach mat like this
http://www.bikinibuys...deco-straw-beach-mat/ could help better. this would help him maintain fitness as well as it would be something that would come for his personal use. Something that's out of leak and he would not like to share anyone else due to sentiments associated with it. At this age, a wallet or watch may not excite him much but a beach mat would definitely do that as the one who is young at heart would love to look young too!