don't you think it's a bit too formal?

and sometimes even a short note can make it really sweet. just need to insert words that are meaningful to both of you. maybe you can make a metaphore or something. for instance, because it's a wallet, an item he will bring anywhere he goes, write a note something like 'so you'll know a part of me is always with you'. and yada yada, something like that. a bit corny, but sweet.