That's tough because the X10 isolates so much and yet has a pretty bassy signature, which is usually more common with dynamic-driver earphones, which in turn tend to isolate less than the X10. I would say you'd have to try one of the few highly-isolating dynamics (such as the Yamaha EPH-100) or go straight for one of multi-armature monsters (e.g. the Earsonics SM2/SM3 or Westone 3/UM3X).
From what I've read the yamahas tend to be a bit finnicky in fit. As I use them at work I need to keep it fairly simple! With regards to the westone 3 recommmendation I did indeed have one and enjoyed it immensely. Right up until the point they went in the wash! Sadly it did nothing for the treble but the bass went on them, hence why I picked the x10 as a cheapish replacement (amazon offer+voucher anyway). Nice to see I was on the right track (backwards!).