I find the ones I use are really good. However, this site:
https://www.tarpsplus.com/collections/clear-poly-tarps
has clear vinyl ones, too. Super clear and pretty strong (though not as strong as those you currently use) They are also more expensive, but they do last. Greenhouse plastic is good for 1-2 years -
maybe 3 (generally - especially with this application), & doesn't have grommets. I have mostly the ones with the string embedded, but have a couple of the others that I tend to use on the south side or maybe on my mobile chicken tractor.
I have also been really happy with the shade 'tarps'/cloths I have gotten from them. My clear tarps with the strings (other than the first set on amazon) have been from them, too. They frequently (if you sign up/create an account) send coupon codes for an additional 10% off your order, and they have such a range of sizes, that you are sure to be able to get sizes that work for you.