Seems like folks are still looking for this part. I drew it up and shared in on Thingiverse.
I've installed it and it appears to work perfectly. Time will tell how durable it is.
Hi Guys, building on Smalthey's design posted on Thingiverse, I have re-drawn his option in Inventor and I also made the model for the bottom part. I can share stl and ipt for both, (top and bottom parts), if anyone interested for further developments. I printed them in PTEG, they looks fair, but I am afraid are not not too strong. Broke a couple during installation.
Coming back to the general topic of this post, I firmly believe Shimano should make these inexpensive plastic guides available for aftermarket repairs. Should Shimano choose to force consumers to buy new brake levers for $60 just because a $1 plastic piece keeps failing (design flaw or incorrect material choice), then consumers should definitely review their buying strategy. Cheers!, Sevciu