advice on miscellaneous Making Shit

Say, hypothetically, you have a MediMemo pill organiser. Say that one of your lids is cracking, and you've previously established that superglue doesn't work, but you'd prefer to replace a single lid than buy (another) whole new set, but using one of your spare lids won't work because you don't have a spare lid for the relevant day of the week and you're That Kind Of Person.

... erm.

Okay, so, you've measured up the lid, and you've established that it's 1.5mm thick all the way along, and other than that broadly a long thin rectangle: 92mm long, with three sections 17mm, HAHAHAHAmm, and 20mm wide.

The HAHAHAHA section is 17mm wide at the top surface and 18mm at the bottom, giving you a trapezoid cross-section.

I am poking at Blender (and goodness but this is Up There with complex but inadequately documented software I Have Known) but I suspect the 3D printers I have access to are not going to be very happy about the required resolution, even if I manage to coax Blender into giving me three rectangles of varying widths and then gently sand the middle section's edges down to triangles. I have limited patience for painstakingly cutting shapes out of plastic sheets and inevitably getting them wrong because my hands aren't steady enough.

Anyone fancy suggesting alternative approaches to solutions? Back of a postcard, etc etc. <3