JST PH 2-pin is what you’re asking for. Regularly use them on 20-28 gauge.
There are smaller connectors, but they have fewer mating cycles and are a pain to work with (tho the ones I mentioned aren’t fun, either). Would recommend 2mm pitch to start with.
They’re very common. Can get a set of 100 connectors for $5ish.
Literally search for “JST PH 2-pin”. Buy a decent crimping tool to save some frustration. Worth the money.
Or buy a set of pairs (make/female) with existing wire leads to start you off and see if they’ll work.