I have done the search for you. YES, there is 3d party batt replacement for your Ticwatch 2 - Cameron Sino CS-GFN405SL.
Original Ticwatch 2 Battery
This is my inflated original battery I just carwed out of my watch, named SP372728SE. I was unable to find identical product on the web, maybe you will do.
The upper one sixth of the battery has taped in some Mobvoi driver, which eats a lot of precious space in your watch. You will need to reuse this part if you plan to get new batt for your Ticwatch 2. The dimensions of original battery are 26.30 x 26.10 x 4.80 mm.
3d party replacement
I got mine Cameron Sino CS-GFN405SL from local reseller for 12$. It is typically meant for an old Garmin GPS System Foretrex 405, but with little effort will fit your Ticwatch 2. The specs are Li-pol 3,7V 290mAh with short circuit and overcharge protection, 29.50 x 24.30 x 4.80mm.