Based on Joel Tellings awesome BRCKT System, I tried to design something similar for 45mmx45mm

To quickly adopt the dimensions you can use this onshape link:

https://cad.onshape.com/documents/ed81ef474513663ac372e0f8/w/8230a2666925ff1adab17ce9/e/7ae79c9b739c86757d2b4fb6

For nice looking surfaces i also designed a support avoidance part, so you can pause your printer, put the part in and resume - but it's not necessary it's just for the perfect look :-)