The first step was to take measurements of the proposed mounting site, the vents on the side of this toaster (don't worry, this area stays cool!)

Due to being completely unequipped for taking measurements in the kitchen. I had to "MacGuyver" my measurements which led to my first failure.

First I traced around the bump-bar to get the general shape for my mount. This is the bump-bar:

I then modeled this.

Next I needed to measure the holes in the side of the toaster. I found that the "flags" we used to poke into steaks in order to label their "cookedness" we're perfectly half of the width of the slanted vents.

Using this information, I squared up a photo I took of the vents on the toaster and then scaled it accordingly using my vent measurements. I then placed the image behind my initial design to sort of "trace" where the hooks should go.

This prototype unfortunately failed. The hooks did not line up properly, something to do with my bodged measuring and scaling. It was certainly strong enough though despite the broken hooks, these broke off under the weight of my laptop in my bag after testing.

Next I had to go back to square 2: redesigning the hooks. This time armed with a marker pen and a piece of paper, I decided to trace the vent holes.

Then, after some painstaking measuring and dimensioning...

I came up with this!

As you can see, the hooks are definitely in a different position. This is promising! I also added grooves for the zip ties to sit in so that the mount would lie flush.

Now to print and test.

And finally, here is the finished product attached to the bump-bar

As you can see, it's much more sturdy than the original solution and should prevent the bump-bar from falling and breaking. It's easy to remove when the work surface needs to be rolled away to be cleaned under.
The benefit of 3D printing this design is that the hooks can be reworked to fit any location or object should the kitchen be rearranged. This also allows anyone else who uses similar bump-bars to create their own using my "hookless" STL file.