Any recommendations for a substitute of the included antenna? Either a base or a portable.
Commercial portable: Nagoya NA-771 (beware clones)
Commercial fixed: Diamond X30, X50 or V2000 colinear.
With any upgraded antenna on a receiver with little filtering like the Baofeng, you may deafen it into hearing no wanted signals if operating it in an RF-hot environment.
Don't transmit without a licence.
For larger handheld or fixed you could build/buy a yagi antenna that has a higher directionality/gain.