Oldcar,
I have seen you all over this site today, you are really making progress. First the harmonic balancer, then the cam gear and now the soft plugs. It looks like a complete teardown to me..maybe going to boil the block! Cam bearings are installed with steel drivers that fit the ID with a lip no larger than the OD. I think you could replace just the one you knocked out, but I am not sure you could buy any less than a SET from your parts house. We always had the block boiled and cam bearings installed by the machine
shop just because it was cheap, he had the drivers and (I think) it was important to line up the oil holes in the block with the holes in the bearings.
You can do it IF you buy ONE BEARING and borrow or make a driver. It sounds like you are going almost all the way on this engine..new soft plugs, new timing gear, timing cover gasket..why not new cam bearings?
Stuart.