Chris, you know that old saying, the first thing to do when you find yourself in a hole is _stop_digging_!
Seriously, just look out for the Nikon 10x CF non infinity corrected lenses (There are a couple of different models, the N and M - with NA of 0.3 and 0.25, both are fine just as long as you avoid the more common modern infinity corrected versions), one of these is almost certainly the first microscope objective you want to start doing this kind of work with!
Re CF and N, I think the N in this case designates a 'biological' objective (Intended for use with light coming through the subject) as compared to a CF-M which I think stands for Metal, where you would expect light to be shone on the subject from an angle close to the lens),
CF means that CA is corrected for purely in the objective, no additional tube lens is expected/required to 'finish' the CA correction. (Chroma Free maybe?)