If they are a dangle type you can swap the clip on part for a French ear wire or a dangle post.
If they are a button type clip some styles can be converted by clipping of and filing clean the clip back and gluing or soldering on a post. Large clips often are too heavy to convert to posts, they droop. An extra large flange nut may help prevent that droop.
It's hard to tell with out seeing them. Take them to your LBS (Local Bead Store) and see if they can suggest the right parts to convert them.