I have an MSR Trailshot, it’s 142g. I’d consider it an essential, you won’t notice it with your 13kg of gear but you’ll be glad of it when you can use whatever water source you find (within reason) and don’t have to go hunting for it or ride way past that perfect site and ride back with 4kg of water.
Mine is part of my ultralight bivi kit, it’s that useful.
Let me know if you change your mind I’ll order one and bring it to you if you end up in Wales 🙂