Telescope seatpost

Dear all,

A happy owner of a Douze Verso cargobike (the Yamaha motorized Douze Heta) since a year, I (1m86) am sharing it with my wife (1m61) to transport our three kids around.

I am slowly getting tired of changing the seatpost height, and as such I am looking to install a telescope seatpost.

I've started to look on the internet but I have the impression that most of the ones with 15-20cm travel are optimized for XC use. They all need either a battery and a remote or a cable to a lever on the handlebar. Ideally, I'd like something simpler, with just a lever under the saddle itself.

Do you know any good reference???

Also, as I live in a very crowded, touristic city center, I am also trying to find a nice electric powered horn. Is there any good one? I think I saw one day an electric horn fitting a Busch&Müller Front lamp but couldn't find the reference...

Thanks for your help!!!