Bantam Magnum 1000 anti-reverse upgrade?

[the legend]

I had a guy ask me if there is a way to install an anti-reverse bearing instead of using the factory dog on an old Shimano Bantum Magnum 1000.  Is anyone aware of an upgrade kit for this or if there is a way to do it with existing parts (of any brand) available?

[oc1]

There is no room in the shaft collar on the head plate for an AR bearing.  A double dog might be possible.
-steve