Not sure if you saw this recent roundup:
13 Packable Mountain Bike Jackets, Tested
There are a lot of choices on there, but I can say of the two I’ve personally tested, the Pearl Izumi jacket is a good choice. It’s not waterproof, but it packs down small and light and isn’t super expensive. The Leatt seems like a good choice too, though I haven’t spent much time in that one. It’s more of a rain jacket and therefore heavier and less packable, but still affordable.