Hi Chris;
I forgot about this company: ZBM2 Industries
ZBM2 Industries
He makes a GMRS+MURS dual-band antenna with BNC
Introducing the Foul Weather QP Whip Antenna – Redefined for Cold Weather Resilience and Maximum Performance. ❄️ Cold-Weather Resilience: Experience uninterrupted communication in chilly conditions with our QP Whip Antenna. The internal sleeve for the super elastic, durable wire ensures no...
zbm2industries.com
He also sells the SMA-M to BNC-F adapter you'd need
Per his description:
The MURS/GMRS is tuned for 160Mhz/460Mhz at 18”.
You could contact him & ask how wide a spread that antenna will do on commercial frequencies