Redragon G49 Pro Disassembly Tutorial | Good 4K Mouse for Cheap
The Redragon G49 Pro provides a solid option to build your own mice with more up to date internals. You'll have to take it apart to do that so here's a video on how to.
I've made free files to use in designing your own mouse:
https://makerworld.com/en/models/527787
You can get it from Aliexpress (I recommend buying from a Choice Store. I went with https://www.aliexpress.us/item/325680...) or MechKeys.