Slim Bumper version of the Surface Duo 1 bumper I uploaded.  This is based off someone that owned a Duo 1 in which they were fine with the fit.  This is two sets of bumpers. One leaves the button area and all the usb area open.  The other covers the Sim slot and the hinge side of the USB area.

Printed in ASA was the best for me, but choose whatever filament you like.  Did not try TPU so don't know how well it would fit. Painting supports on the ends will keep the curved end shape better.  Will need double sided tape to stick to the Duo.

https://www.amazon.com/gp/product/B019OQ4ZG0/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Let me know how the fit is for you, thanks