shifter acorn nut

Well, I just got out for a day trip, pulled off a ramp,
downshifted into first and stopped. The shifter
was completely loose and I couldn't shift. Pulled
over to a parking lot to check it out, and I lost the
little acorn nut that connects the shifter to the link
bar (i.e. the part where my foot goes disconnected
from the shift linkage).

Anyone know what size nut this is? If not, I guess
I'll go buy an assortment to see if I can get one on
before I lose the day.

'07 Rocket III Classic, 350 miles.

Looks like it is M6-1.0, at least that seems to fit.
Little lock tite on that bugger should hold it until
its first service when I'll ask them to put a proper
nut back on it.

Same thing happened to me. Replaced mine with a nylock nut, seems like I used a 1/4 20 but I'm not sure.