The Standard Horizon horn works well. Holds up well also -- hasn't yellowed or failed from UV exposure. It's just a speaker so it will work with any bran radio.

I had a prior horn that didn't last 3 years and cracked due to UV, but the SH horn has been in use for 7 years and still looks good / works well.

The VHF also has a "yelp" type siren function. In the harbor it's fun to see jet skiers slow down and look around when I give them the siren (just for a second or two so they can't pinpoint its source).