Yes. In fact, most opals end up cut to calibrated sizes. The
freeforms you have seen were most likely very good quality opals
that the cutter now some sources?
Go to a major gem and mineral show, i.e., GLW or International,
and you will see plenty of opals in all price ranges. For a ring
you might want to think about a doublet faced with quartz. They
give you the true opal look with the durability of quartz.
Be aware though that opals are highly addictive.
Mike in Maryland