Take it to a arborist that deals in bonsai trees. Or to a conservatory that has their own botanist they will usually be more than happy to help with identifying a plant/tree. I called the one we have and they helped with information on how to cut the roots on my sycamore tree in order not to harm it. I was removing a sidewalk and needed to remove the roots under the sidewalk to be able to replace it .
I agree with Nomad1, take the bonsai to a professional but if you can't, just go online. The first thing I would do is determine if the tree is temperate or tropical.