This is a remix! The original design, to attach the buffer of the MMU3 at the rear of the enclosure, was already quite good. But unfortunately it was not suitable to attach the buffer at the side of the enclosure since it interferes with the transport handle and the (un)unoriginal drybox (when mounted on top of the enclosure).

Thus I redesigned the model. The bracket is attached at the right side of the enclosure. The front panel of the buffer faces backwards.

For installing the buffer with this bracket to the enclosure you need:

2 x M3x12 bolts (to attach bracket to enclosure)

2 x M3S nuts (put it into the bracket)

2 x M3x40 bolts (to attach bracket to buffer at the spacer)

Concerning the additional spacer:

You need at least 2 spacer parts. I printed the spacers for the buffer plates six times and replaced the original provided spacers. For each spacer you need:

2 x M3S nuts

2 x M3x30 bolts

(except were the bracket is attached to the spacer, there you need the M3x40 bolts.)

As top cover for the buffer, as seen on the picture, I used this design:

https://www.printables.com/model/565759-prusa-mmu3-buffer-top-cover