I’ve been running the cheap eBay ones on another bike for years with no complaints, and I bought compatible cheap ones on Amazon for the Grom.

These are about as budget as they get, but all of the cheap ones are essentially the same.

https://www.amazon.com/Fireyouracing-Clutch-Handle-2019-2020-levers-Chrome/dp/B098CB9SXV/ref=mp_s_a_1_14?dchild=1&keywords=grom+levers&qid=1631222166&sr=8-14