Here is my model of a bed mounted handle for the Ender 3 (or Ender 3 Pro). This is not a remix, it is something I started from scratch and modeled to look like other handles that are already available, but better. I created this because other models were all lacking structural strength. I printed two different models that I found on Thingiverse, and both snapped during normal hand-sanding, so I decided I needed to make my own.
This handle comes in three flavors:
Handle with Reinforcements
Handle with Reinforcements and Cam Mount
The ‘Handle’ is almost identical to handles that are already out there. ‘Handle with Supports’ is the standard handle, but with four additional reinforcements to limit flexing and add rigidity to the print. ‘Handle with Reinforcements and Cam Mount’ has all the reinforcements from the last model, but adds a mount for a Pi Cam v2 housing created by sn4k3 (https://www.thingiverse.com/thing:2987719). For a Pi Cam v1, use the housing created by Modmike (https://www.thingiverse.com/thing:2886101). I recommend also printing the extension arm created by The_Joy_Of_Printing (https://www.thingiverse.com/thing:4221931)
Something I noticed with other Ender 3 Bed Handles is there were some incompatibilities with slicers (or at least Cura). In my comparison picture, you can see the difference between my design and other designs when sliced. If you look at the support structure for the other handles, it is sporadic and does not follow the lines of the model like it should. This likely influences the structural integrity because it does this same thing in multiple places on the models. From hours and hours of modelling this handle, it appears to be a problem with others adding ‘Fillets’ (rounding) to the bottom edge of the model, so my final models leave that out. I was able to round most of the other edges to limit any hand-sanding you might want to do for comfort.
The only setting I recommend changing in your slicer is the shell/wall count; raise it to three (3) to increase rigidity.
As always, I have included the STEP files for all these handles in case anyone wants to remix them.