You might want to be a bit more detailed in the description of what you're looking for, besides "light and compact, works with electric and upright". Is it just for practice, for instance? People kinda need to know to give useful advice.
Taking your "light and small" statement literally, the most compact bass amp I've seen is the Roland Micro Cube Bass RX (on the right in the picture).
About a foot tall, can be battery operated, comes with a few probably good-quality effects (Roland is the same manufacturer as BOSS pedals). Also has headphone outputs, line-in input, built-in chromatic tuner and metronome, for practice. Pretty much the perfect amp to noodle in your bedroom at two in the morning without disturbing the neighbors, but I'm guessing not much use for anything else.
I got an even smaller guitar version of this, and it's a surprisingly good practice-by-yourself tool. It's even much louder than it looks for the ridiculous size, but worthless when any sort of real volume is needed. Goofing around with a drummer? Maybe if he's playing an electronic drum kit, and doesn't mind using the volume knob. I imagine the bass version is pretty much the same deal!
But I'm guessing this has nothing to do with what you're really looking for. Am I right? So tell us more about what you really want!
