I was going to suggest old, but reliable 1990's tech like a Ramsey FM-30, but Amazon has a bunch of Far East sellers out there, [www.amazon.com]

From what I've read, these are a bit spurious, so I would recommend building a Low Pass Filter for harmonic suppression. If you add a linear amp to that, you could build the filter in there. Just as a suggestion. Good luck, as the FM free radio political climate really sucks today.