There are work-arounds to this limitation. Find places that allow you to have yard sales at their business on the weekend.
I've found several inexpensive ones that have them in Boulder County.
- Tables to Teacups - held the last Sunday of each month. April 29 - Oct 28. Setup starts at 9am with no early setups. Spaces are not pre-assigned. Bring your own tables, chairs, tents, and change. Spaces are limited and can be prepaid in person or on the website. Tear down and cleanup must be completed by 4pm. $10 for 10ft reserved in advance. $20/10 ft day of. 1420 Nelson Rd. 303-485-7270
- Lafayette Flea Market - held every Sunday while the weather is good during summer months. Setup starts at 7:30 am. Vendor/Seller spaces are assigned and can be prepaid in advance. Opens to buyers at 10am. $10 for two parking spots. Bring your own tables, chairs, tents, and change. 130 E.Spaulding. 303-665-0433 Facebook: Lafayette Collectibles & Flea Market.