Then you don't want a 3.5mm jack...
Me? I'd cut the power lead and rejoin it with the conductors reversed. Twist & solder the conductors, and tidy it all up with heatshrink sleeving.
If you're missing a trick, I am too!
Not for IEM's, but I've tried all manner of ear buds with my mp3 player, and just can't get on with them, for exactly the same reasons.
Peavey ValveKing Royal 8.
Nice little 5W valve combo. In very tidy condition, all working as it should.
£45 collected from my place near Royston, Herts. Happy to arrange delivery.
Because that's what you told them?
From their Terms & Conditions of Sale:
---x---
1.5 RS is a business-to-business supplier. The RS website is intended for use by business customers and not by private individuals acting as consumers (“Consumers”).
---x---