Unfortunately I've seen "wide bore" tips in all shapes and sizes, none of the ones from my various Mutations (all clones, including a Yep that was advertised as a MXv4 or MXv3) or any others seem exactly the same.
If you have any shops nearby, you may want to take the top cap in to show them and see if they've got anything to fit. If it's an authentic, you might contact the manufacturer...good luck, and congrats on breaking through the lurker barrier after a year!