I don't think you can but anything without a floor is going to be almost impossible to keep the rodents out. I had a pop up blind setup and had a skunk nose in looking for a place to get out of the rain.
You could put the tent up on a floor, would be cheaper than $1000 and may be possible if you are driving to the site, just a few pre-made floor sections. That would keep you up off the ground a bit and have something to lay the tent down on, may reduce the mouse issues.