Fluorescent light fixtures have always been a source of EMI. It's best to avoid them completely if EMI is an issue. The electronic ballast probably just increased the level or changed the frequency of the EMI being produced.
Filters, chokes or shielding may make an improvement or maybe not. The tubes may be emitting interference, in which case the entire fixture would need to be shielded.
I would try a halogen or LED fixture. LED fixtures have power supplies but they are designed and operate differently and at different voltages. If it is the tubes emitting the interference, an LED fixture will remedy that. Halogen is another option but they are significantly more expensive to operate than LED.