Now try getting the silicone high-heat O-rings in Uruguay. Do I go to the rubber-products neighborhood, the auto-parts district or look for a gaskets and seals seller behind a barraca?
I supposedly have twenty o-rings (2 sizes) coming from eBay, but as tracking shows them still bouncing around China after a full month, I am thinking I will need to order from the States.
Ten 75 durometer for $6.25 with free US shipping from
https://www.ebay.com/usr/oringsandmore, go here for
listing details
I ordered some 20 mm O.D. red silicone O-rings with 3mm cross -section (14 mm I.D.) and also ordered 20 mm O.D. ,2.5 mm cross-section, (15mm I.D.) A diligent eBay search may turn up a US source better for you for buying fewer.
My variously sourced Solo stems vary slightly in diameter between 14+ and 15- mm; some are OEM and others from China at various times.
These O-rings will also work to hold my Solo stems in my Boundless Tera (a fine convection heater for Solo stems.)