This week, I upgraded the MK8 extruder in my Wanhao Duplicator 4X to the MK9 version, with a kit purchased from ultimate3dprintingstore.com
Unfortunately, when I tried to put the top cover plate, I noticed that it didn't fit anymore! The new extruder has a "bulge" at the top that doesn't allow the original plate to attach properly, resulting in a loose piece that might fall down during printing.
The piece (sold separately!) costs $15 for the plastic version and $30 for the aluminium one.
So, I decided to search in Thingiverse, and although I found a lot of innovative designs, none of them could fit in my 3D printer: The holes for the screws and filament guides didn't line up properly, or the size was too big.
In the end, I decided to make my own, and I'm sharing it in the hopes that it might help someone in a similar situation. If you need this part for a quick replacement, use the following settings:
ABS, 10% infill
No raft, no supports
Bed temperature: 110°C
5 solid top layers
2 outer shells
And it should print in an hour or less, with enough strength to be reliable. If you want to use it as a permanent part of your printer, increase the infill to 20% and the solid layers to 10, both in the top and the bottom.