Welcome to TalkBass Drausin
You have to forgive the average TBer's, their reading comprehension isn't very good
The requirement for operating with battery power will either sound rather wimpy, or cost a fortune.
There's tons of threads on TB about using inverters and car batteries with regular amps, but I have a hunch that You want something a little bit more portable?
In my very limited experience on battery powered amps, the Roland may be Your only real choice. Reasonably priced, good reviews and the availability is good.
While I totally agree that an ABG can't compete with an acoustic guitar, they're fun to noodle with and if the guitarist has a bit lighter touch, there may even be a slight possibility of some balance.
IME You can forget any gigging you wanted to do as well as jamming, without amplification of some sort though.
Do keep in mind that some city regulations prohibit the use of any
amplification, some allow internal battery operated amps.
A DB is always an option...
So, if You give us Your price range/limit and the weight limit, people will be better able to give suggestions about what to try out or buy.
I'd guess that the Roland is Your best bet though.