Even though I'm not active on this forum anymore, I still own and daily drive this explorer after all this time. I wanted to come back to post that I have found a factory cabin filter that fits the dimensions for this mod exactly! The filter is for a BMW 3 series I believe. I am now using a WIX 24784 filter, which filters bacteria, mold, mildew, algae and yeast. Here is the rockauto link. I feel silly for making my own filters previously.
More Information for WIX 24784
PICS:
This tag must be cut off with some pliers for the filter to slide in. Took me just 5 seconds to fix it:
Filter installed!: