Attaching new wire to original antenna

Having trouble finding the right connector for the ol' antenna. The original wire wasn't completely there and had been cut. I ran a new wire from the radio to the inner fender.

The problem is that no one has the right size adapter to plug into the original antenna base. The adapter I bought is too small (photo 2). Does anyone know where I could get the right one?

The last photo shows the final connection that goes to the radio.

Thanks