I ordered neoprene(NBR) and silicon O rings from ALIEXPRESS, 22x14 mm. SkyCable Store. First I tried the silicon, supposed to withstand 200 deg. C. It did not stick, but Wear and Tear were excessive after one flight only. As a last resort and nothing to lose feeling I installed the NBR, rated to 100 deg. C only. The best. Not sticking, not leaking for 30 flights, some droplets after 35. Pack of 10 units for 93 cents, postage one dollar more.