This is a mount for a common humidity/temperature gauge (Available on Amazon https://www.amazon.com/gp/product/B07YWVN74P/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) for MK3s in an enclosure.  

This one let's me know the temperature at the top of enclosure.  I have a stand-mounted version as well that let's me know the temperature at the bottom of the enclosure.

I've printed it in both PLA and PETG without issue.

I used a brim and set the elephant-foot compensation to 0.  The chamfer on the bottom eliminates the need to trim any “flash” left over after the brim is removed.  I'm not sure that brim is required, but better safe than sorry.

I've included a STEP file (Originally designed in CREO Parametric), STL (Imperial Units), and 3MF (PLA).