Usually with the LED Retrofits for Fluorescent, you have to bypass the ballast anyway so that could be a decent option. Or depending on the fixture, they may have an incandescent equivalent where you could just swap a part or two.
In this house, all 4 bathrooms had the same fan/light combo from Broan which used a 2-pin square fluorescent bulb with a ballast inside the fixture. They flickered horribly and took a second or two to start, and of course weren't dimmable; so I looked up and found the equivalent fan/light combo in the non fluorescent model and it turned out to be an $8 part that was literally a 20-second install per fixture - no wiring, just plugging in the housing - and now all for are regular Edison Incandescent bases running the Cree 60W TW bulbs and my SA switches were reprogrammed with Dimming enabled - much nicer experience.
Or of course, depending on the fixture, it probably wouldn't be that hard to just swap it out with something more efficient.