That toner cartridge looks like an awesome base for a pack.
Here's my advice on finding parts & greeblies (or at least here's how I do it)
First step: Never throw anything away. That being said don't turn into a hoarder but before you throw anything away, no matter how mundane look at it with fresh eyes. Ignore what it is and look at the basic shapes and oddities of it. If it's something common then think of what it would look like with part cut off. I have 3 or 4 totes full of random crap that nearly makes it to the garbage can but then I kind of turn it over a few times and look at it's greeblie potential then either trash it or toss it in the totes.
Second step is the same as the first but in a store (generally a dollar store, don't want to pay much for greeblies). Again the key here is don't go in with pre-conceptions just look at the items, any items, and try and see their potential uses (beyond what they were designed for). Certainly if you have a plan go looking for what you're after but maybe another day go in with a clear head and no plan and see what you can find.
Final step (also ties into the first): If something breaks at home or work and it's going in the trash...take a few minutes to disassemble it. The insides of things are treasure troves of parts. I work for a car dealership in the parts dept so I usually have a box at work where I take apart components that are getting trashed and I keep anything neat looking.
Not sure if this will help you, and I know it sounds like I'm a hoarder but my greeblie bins are free to peruse for any of my local costumers so it doesn't get too bad (not sure the wife would agree though)