A plan fluorite should do a decent job, per se, since the field is supposed to be very flat, and 532nm is pretty close to the design center wavelength for the chromatic aberration compensation. I believe a 10x might be a little bit on the light side, but it's worth a try.
If you decide to pick up another objective based on the results, go for an infinity corrected plan achromat dry objective. Shorter working distances usually translate into the objective using additional meniscus lenses on the end your beam will exit, which will translate into a lower effective f/#, better focusing and shorter distance to the focal point.
Additional benefit can be had from picking up a pair of lenses to expand the beam to fill about one third of the aperture of the microscope objective. Anchor optics has a series of good achromatic doublets (incl. negative achromats) in the experimental grade part of their site. Just make sure you get the first grade ones. CVI Melles Griot has a PDF that is equipped with all the formulas you need to design a beam expander. The shortest one is the negative-positive combo, but if you can't find a good match of lenses, the other one is more flexible in that regard.
I may decide to work on a dedicated head for burning with greenies, if my interest in optics sticks for long enough to do a good job of it. A group buy might bring the price down significantly. Don't hold your breath, though. I'm not always able to retain focus on more than one thing at a time, and the principal focus atm is in ophthamology.