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I’m not sure if you’ll find out more on this path, but wanted to mention that a while ago, some people seem to have found out the actual producer of Fairphone’s TWS earphones. Maybe that gives you more information to track down parts information.
Other than that, Fairphone recently informed that they are planning to offer some individual elements of the TWS earphone set in their spare part shop. However, I would rule out that this will include such tiny parts – most likely they will only offer the complete case and individual R or L earbuds and/or the silicone buds.