After searching long and hard to find the best covers for our own speakers, we finally settled on Wake Specialty's covers. They're the best fitting, best made covers we've seen, and have great features like a Teflon coated front panel for easy clean up of bugs and road debris, and a mesh insert for drainage.
We haven't imaged the NVS covers yet, but you can see what they look like on Fusion's T-Series 5.25
here.
The covers for the Addictions are available for pre-order
here.