O rings that should work:
https://www.amazon.com/Nitrile-Rubber-Rings-Metric-Sealing/dp/B0BFMWKP79/
https://www.amazon.com/uxcell-Rings-Nitrile-Rubber-Diameter/dp/B07W72F7RF
https://www.amazon.com/uxcell-Silicone-Outside-Diameter-Sealing/dp/B07CVJMGMM
Too thick? Try this one- https://www.printables.com/model/434344-bic-2-smokes-case-print-in-place Not air tight but very slim.