I honestly just bought stuff off Amazon of eBay. This filter had the 300 KHz bandwidth even though it says 10 MHz (you might not get sent the same filter with these sorts of merchants, though, and they may not know what they are selling):

https://www.amazon.com/Stable-Interface-Anti-Interference-Bandpass-Frequencies/dp/B08KZNLZWL?ref_=ast_sto_dp

I have this amp and a few others like it:

https://www.amazon.com/Jadeshay-Noise-Amplifier-50M-4Ghz-Amateur/dp/B0BTBZXHN4?ref_=ast_sto_dp