I didn't like the Velcro, but I have faith in Mr Speer that I may, one day prefer it. So, I made a completely reversible mod to add a zipper. It's so simple I'm sure somebody else has done it.
I bought a 100" zipper from Amazon (like $8). Make sure it has a double sided zipper so you can open and close it from inside and outside your peapod. I bought at least10 feet of sew-on hook and loop (AKA Velcro) not the stick on kind , you'll see why later. And I sewed on the Velcro onto the zipper so I can just insert it into the peapod Velcro as an adapter of sorts. I'm too lazy to describe the steps, but they are obvious and easy and took me 15 minutes. You just need to plan your placement of the Velcro on the zipper so there is a little overlap to prevent breeze through the zipper (not even sure that would happen).
The best part is that you can now open a breathing hole to prevent moisture buildup inside the peapod by opening the Velcro along side the zipper just where you want the hole. But, you can still unzip from top to bottom to get in and out.
Not sure why speer doesn't sell this already. Comments please.
Will add images shortly.