I got material from Hobby Lobby (which is a water resistant type material) with my 40% off coupon on my Hobby Lobby app, and in total it only cost me about $6 or $8 to make my own.
Here is the one I came up with. (Sorry, not the greatest lighting for these pictures)
I am so excited to have this for our trip and even happier I was able to make it for cheaper than purchasing one. It was a fun project and I think it came out nicely. It folds up nicely with the stroller so I won't have to remove it if I choose not to. It also goes on very easily, so even if I do remove it, it only takes about 2 seconds - literally - to put on or take off.