It doesn't sound like you need mic pre's, reverbs or much in the way of EQ. If size/weight is your main concern, Samson makes a smallish, battery powered PA speaker that's small, inexpensive, fairly loud, cheap $250 and rechargeable.

https://www.amazon.com/Samson-Expedition-Rechargeable-Battery-Bluetooth%C2%AE/dp/B00HXE4BVU/ref=sr_1_3?ie=UTF8&qid=1477688095&sr=8-3&keywords=samson+xp106w

This is not rip roaring loud but will work for most music.

Marshall makes various outsized bluetooth speakers that might be powerful enough:

https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=marshall+bluetooth+speaker

Alessis makes the Transactive. $200 and probably as capable as any of the above:

https://www.amazon.com/Alesis-TransActive-Wireless-Bluetooth-Rechargeable/dp/B00BPQ9SHO/ref=sr_1_1?ie=UTF8&qid=1477688400&sr=8-1&keywords=alesis+speaker

You can find this Transactive under another brand I can't remember for $99, so that's probably the best deal.

You can get started with one of these options, see if playing the streets is for you and then, think about upgrading to something that'll make great sound. Any of these options should be good and fairly loud before breaking up.