Good question - although the screws are extensively documented, they’re hard to find. Fasteners Guide - Framework Guides
You need MHF4 connectors but any antennas for WiFi/Bluetooth should work:
Probably best to get an MHF4 to reverse SMA cable and an SMA antenna (search and you’ll see various sensitivites in dBi - larger ones are more sensitive).
You might also be seeing a USB wireless adapter with large external antennas:
https://www.amazon.com/Techkey-1750Mbps-1300Mbps-Antennas-Wireless/dp/B07PKMFPF7/