Yes I saw that one it does seem strange most of the other ones seem to be readily available.I found a couple different listings but only on Indonesian sites, I imagine that's where it's being manufactured and it hasn't quite made it to major distributors yet, none I found ship direct to UK.
In stock at FT and a bit cheaper
https://www.fasttech.com/product/9728429-authentic-vxv-soulmate-rdta-rda-pod-cartridge