[manwithredbike]

I have some 6 core alarm cable lying around in the shed. It's multi stranded so flexible enough but wouldn't carry much current. Outside sheath diameter overall only 4mm ish.
If any use, if you can't get sorted, let me know and I'll post you over some of the roll

Edit. The current carrying capacity on alarm cable wouldn't be much more than an amp or so but presumably the sensors are low power/current and your be fusing them accordingly.