Here is my take on a Prusa MK3 Enclosure.
I used 1" square extrusion for my enclosure. These are the accessories I put with them.
Handle with alignment stripe for 10 series
Here is an handle that fit on the 10 series of aluminium extrusion. Use 2x standard economy t-nut. I spent a lot of time making it support less, supports are a waste of time and material. I did not print it 100% and it's still really robust since it's printed on it's side. It got a small notch so you can position it right in the middle, thanks to my small OCD.
Corner Panel Mount Series 10 & Panel Drilling Jig
It's used for mounting a panel to a extrusion enclosure. It's flush with the extrusion if you use 3mm or 1/8. I use a #12 x 3/4 screw to hold it in each corner. I print it with 100% infill for structural strenght and because it's already optmised for less material used. Use the provided panel jig to drill the hole at the right place. Easy print, 100% infill, 0.2mm layer height, no support.
3 Way Connector Extrusion Series 10 & tapping jig
This print is used to attach 3 extrusion together to form a corner. I use this instead of buying one because they are really expensive. You just need 3x SHCS 1/4-20 x 1/2" and thread the center hole of the extrusion. Easy print, no support needed. 0.2mm layer height, 100 % Infill.
I spent a lot of time making it support less because supports are a waste of time and material.