I would think that "clip ons would be a bad idea since they probably wouldn't cover your peripheral vision or over and under your glasses.
As Hak mentioned, most laser safety glasses/goggle makers have "slipovers" which can be worn with prescription glasses.
Edit: Survival Lasers has a good selection of reasonably priced, high quality safety eyewear.
In which color do you want safety glasses? I saw different colors of safety glasses on Reecoupons, I don't have any info about what color is suitable for different lasers, you can explore there, I hope it will work for you.