i know it’s the older I spec b, but CRC have xt m8000 rear shifters for £17.99 plus an extra    10% off, so just over £16. I picked one up for my ‘spares’ box. Thought it might interest someone.

https://www.chainreactioncycles.com/shimano-xt-m8000-11-speed-trigger-shifter/rp-prod135894