FP3 blinks red fast, doesn't charge (in Costa Rica)

At this point I would stop using the USB port to avoid potential further damage to the phone.

To get by for the moment, there are external universal smartphone battery chargers, here’s an example … External universal chargers for Fairphone batteries … but there are many more of them, you just have to make sure that the charging contacts are slim enough to make contact with the Fairphone 3/3+ battery contacts.

The USB connector is in the Bottom Module.
You could ask vendors who ship internationally, like e.g. Vireo … https://www.vireo.de/smartphones-zubehoer/fairphone/ersatzteile/8762/fairphone-3-und-3-bottom-modul … (clove.co.uk doesn’t list the Bottom Module currently, it seems).