Not a Mechanic I take it .
threadless steerer spacers only function as vertical compression between the top cap thru the stem to your upper bearing race

there is no torque on them individually so friction between them is fine.

just as a whole combination is turning with the fork gripped by the stem.

all those 22,2 7/8" things in 2nd post grip the stem quill . you talk about a 9/8 fork.



I dont see the J&B/ origin8 thing , show it to me.

going to add another band thing for the cable stops ? both need to grip the steerer tube.

IDK if off the shelf stuff will be perfect enough .. take some risk, and buy it and report back..

I got along fine with bar end shifters , I had a firm grip with both hands while changing gears.