I agree with
@Wraith and 100% encourage building your own. I personallyI use 2 Pavo20 and 2 cinelog30 v3 for my cinematic work drones despite having a pretty large custom built fleet. The Pavo20 pnp without the air units are only ~$120 us, thats definitely the cheapest/quickest/easiest way ive found to have several backups on hand at work sites.
Without knowing anything else, just that youre coming from an avata, I would not recommend trying to build an analog, gopro carrying cinewhoop. There are a lot of considerations to that and it would no longer be sub 250g, which has legal tradeoffs that defeat the purpose of having prop guards in certain countries. Mostly though, it would fly very, very different from an avata.
also, just in case anyone was wondering, the avatar/prebuilt DJI drones use the o3/o4 "transmission systems" which are technically different from the o3/o4 air units. I dont know how/why they chose to make it like that though.