[porschefan76]

Hi. It looks like they're M18x1.5. Here's a link discussing:

O2 Sensor Thread Size?? - Pelican Parts Forums

Looks like Amazon has them and with Prime shipping:

https://www.amazon.com/M18X1-5-Oxygen-Sensor-Plugs-Exhaust/dp/B07VD5MK3X/ref=sr_1_2?dchild=1&keywords=M18x1.5+sensor+plug&qid=1615950423&sr=8-2