The cooler master MM710 has a good sensor, small circuit board and you're able to get it in clearance most of the time (got mine for 25 euros). This makes it the perfect candidate for making a way cheaper version of the Zaunkoenig m2k (mouse that weighs 24 grams and costs 300 euros).
I didn't want to knock off the shape entirely so tried to keep it unique. The design can be printed without the use of support (mouse buttons on print bed) and doesn't require extra things for assembly, only the 2 PCB screws from the MM710 and its skates (but buying aftermarket once is recommended).
The design could still use some improvements, but it works for now might update it later.
Known problems: a bit of pre-travel on the mouse clicks (but weight of your finger takes care of that) can easily be fixed by extending the sticks(?) underneath but haven't tested the new length yet. And the scroll wheel isn't held in place so if you want to click you need to do it precisely from the top but it's still perfectly usable.
UPDATES:
The author marked this model as their own original creation.