There are some clear tarps out there and there are some places that will make you custom sizes. It is essentially greenhouse clear plastic that has reinforcing grid rope like stuff inside of it. I know of a couple people who use them in winter and they love them. You can find them by doing a search for things like reinforced greenhouse plastic, clear tarps, etc.I haven't gotten mine put up yet. Still waiting for it to get more wintery, lol. I do plan on using screws and washers to put it up though, to help keep it from tearing. I got the heavy duty shower curtains. I would like to use tarps, but I don't know if/where you can get clear ones.
I hope to get some at some point, but because we have more than a dozen runs that need it, it is going to be pricey for us. So for now I just use painters plastic dropcloths and hold it in place by screwing pieces of 1x2s over the top of it to keep the south winds from blowing it off. The north/west winds are ok, but when we get the weird south winds it tends to rip plastic through the staples, so the wood pieces keep it in place.