does anyone know of an indoor bonsai that can cope in shadier conditions?

There may be a few species which can survive indoors in the shade, such as
Ficus, but they will make very poor bonsai. The whole idea behind bonsai is to
grow a tree with the smallest possible leaves, twiggy growth, & short
internodes, which require the maximum amount of sun the plant will tolerate. I
suggest you forget bonsai and stick to Aspidistra & Philodendron, unless you
can set up a fluorescent light fixture indoors & find an outdoor location for
the summer.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)