Cabela's, Midway, Brownell's, and many others who offer hearing protection products would be a good place to start. You can read the descriptions of the products and often find a reference to a feature that allows use with a radio.
I go to websites like these to discover brand names in a product category and then go to the brands' websites to see everything they offer, not just the models that Cabela's, et al. choose to offer.
If I find a brand and model that I want, I google it to find the best price from a vendor I think I can trust.
Good luck.
