Handsfree SpeakerPhone Help

Hello, my father is a long distance flatbed truck driver and I am looking to get him a hands-free speakerphone. I need something for him to be able to safely make calls and he refuses to wear a headset because he says it is uncomfortable. I bought him the "Jabra" and "Motot305"(I think it was called), however he told me both of them are too quiet.

Which brand/model should I get? Is there anyway I can hook his phone directly into the radio?

Thanks