For portable you could buy a Diamond antenna but beware of fakes (https://forums.radioreference.com/threads/how-to-spot-a-fake...) See that you buy one with the right connector (RP?, male/female). I have an srj77 from diamond on my anytone that fits and works fine.
For larger handheld or fixed you could build/buy a yagi antenna that has a higher directionality/gain.