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This was the next model. I haven't tried them but look pretty similar. Also out of production though but probably a bit easier to find second hand.
https://www.amazon.co.uk/Sennheiser-Wireless-Bluetooth-Headphones-Compatibility-Black/dp/B007K3SB6KBe aware that they had wired and wireless versions of these so you need to be careful which you are getting.
I don't think they have a modern equivalent.
I have a set of these which are by far the best gym headphones I've owned. https://www.whathifi.com/sennheiser/pxc-310-bt/review
Compact and don't move about at all with good sound quality and noise cancelling. The downside is they are out of stock so you have to hunt for them second hand (I've actually bought a second pair for when the first die).