Some ideas:
Make it more of his problem. Right now, when he goes out,99% of the time he will be fine. Its that 1% he has to be prepared for. Teens are notorious for not being able to consider the level of danger.
So make it his problem if he forgets it. Tell him that you want him to be able to go to Jamaica and to college, but that he has to be able to have his epipen with him at all times as the environment will be much less controlled as it has been growing up. So to prepare for that, you want him to have his epipen with him at all times now.
Say that if he forgets once, then you will interrupt what he is doing and bring it to him.
if he forgets a second time, then he has to come home from the activity.
Tell him you don’t want to punish him, but if he can remember any time where he has eaten the allergen and how bad that was,…you want to prevent that. But he has to take charge.
Also have a checklist for him…Phone? Check. Epipen? Check. Wallet? Check. Keys? Check.
Have him brainstorm how he can carry everything. Cargo pants? Something that attaches to his belt? Backpack?
Keep in mind that for Jamaica that the epipen might get hot…so he might want a frio pack or somethign to keep it at the right temperature.