I bought Spank Lock-on grips (https://spank-ind.com/products/spoon-grips), but they came with just one lock-on and an alloy end cap. I needed two lock's because I have bar-ends.
I designed this part as a replacement. It uses a M3x14 screw, while the original uses M4 threads. It seems to work fine.There were printed in PLA, I don't know if they will be durable enough, PETG or ABS would be stronger...
I've included the openSCAD file, but this one contains some hardcoded measurements.
To make it sturdy I used full infill and more shells (4).
Also I printed it with high resolution for a smooth finish.
No need for supports, the overhangs should be easy to print.