Summary

You can access the CAD source with a free OnShape account and this link:
https://cad.onshape.com/documents/1f97201db151ffff180e9eb8/w/ed431e8f40d477a947024067/e/d734e1175cff8b490886d382

I'm a big fan of OnShape because the interface is intuitive, I was able to learn it in one evening after watching the tutorial videos.

This part was designed for PLA, and printed on the Mini shown in the pics. If you're printing with PLA, make sure it's true PLA, not a PLA blend like eSun "PLA Pro". I know the cables are messy in these pics, I'll do cable organization later.

Here is the Amazon link to the camera I'm using. Because the camera cable is ribbon style, I chose to conceal the cable inside the RasPi case and attach the camera directly to the case using foam-backed two-sided tape. The stuff is crazy-strong.
Camera: https://www.amazon.com/gp/product/B012ETE75I/ref=oh_aui_detailpage_o02_s00
Tape: https://www.amazon.com/Scotch-Extreme-Mounting-60-Inch-Black/dp/B005SRECEU/ref=pd_sbs_328_6

The fastest way for me to complete this project was to attach the RasPi to the arm with more of the same tape. Since I'm generally impatient, I don't like waiting on hardware to arrive in the mail, so I try to avoid hardware requirements when possible. But for this I did use two of the holes on the side of the LulzBot Mini frame and I found some 3mm x 12mm machine screws at my local OSH.

This design could be adapted to connect to the bed instead, by creating a new base section. Since I'm not doing time-lapse, I chose to mount to the frame since it's easier to design for. I have the concern that PLA may get weak if placed close to the heat of the bed during operation.

You can print however many arm segments you want or just extend the neck of the segment to make it longer. The friction of the joint is important to support the weight of the camera + RasPi, and you can alter this variable by changing the values of the two dimensions shown in the last image, these are found in Sketch 1 in the OnShape document.