Current off the shelf HDMI port savers a.k.a. HDMI Locks for DSLR cameras are quite expensive. Here, Vimeo member Kenrik March shares a simple method to lock down your HDMI cable. The simple clamp will prevent your cable from being shifted left/right/up/down/forward/back. The use of clamps and spud may not line up perfectly with every HDMI output port on every camera, but it's a good starting idea on how you could go about making your own and refining the process. [Thanks Kenrik]
Cheesycam DIY HDMI Lock
I was actually working on my own version which uses a 15mm OD Collar around an HDMI cable. Once the collar is placed onto the cable, the collar then sits inside a 15mm 90 degree clamp. The clamp obviously can be adjusted to fit any camera in the world, but you'll need a set of rods to use this technique.