Neale,
There were chrome, domed end plugs with rubber expanding grippers (expanded by an allen screw in the end of the plug) fitted when I got the bike - not true bar end weights, though quite fairly heavy in themselves. Bar end weights are normally used to counter high frequency vibes - is that a problem for you?
My standard SFC1000 clip-on ID is 18mm but it has been newly powdercoated and this has gone into the tube; though not a thick coating, the true bare metal ID will consequently be fractionally more than that.
Hope this helps,
Regards, Andy