Amazon with huanlemai has the Dinhand Patio Umbrella Mosquito Net w/ Double Zipper Door for $29.99 - 5% off coupon (click apply or checkbox) - 50% off with coupon code 50NFF8UG in cart = $13.49 with free shipping on $35+ or with Prime.

Fits umbrellas from 7.5 - 11 feet. Has weighted led bottom and 6 pockets for additional sandbags.