I tried these amazon orings in my 3s shocks. I could only fit 4 orings in per cartridge. They stopped the leaks, however there was too much resistance on the shock shaft with the bigger orings and made the shocks much stiffer.I used this size and was able to fit 5 per cartridge. You can reference that size and find something local to you I’m sure. My shocks have been bone dry for months now, even after bending several thousand shock shafts.
uxcell O-Rings Nitrile Rubber 2.6mm Inner Diameter 7mm OD 2.2mm Width Round Seal Gasket 50 Pcs https://www.amazon.com/dp/B07X2Y4956/ref=cm_sw_r_cp_api_i_XFTxEbS6GV918