AC WORKS 10ft NEMA 6-20 Splitter 10-ft 12 / 3-Prong Indoor/Outdoor Sjtw Heavy Duty General Extension Cord in the Extension Cords department at Lowes.com
Cable Matters Outdoor Rated 12 AWG Heavy Duty 20 Amp Extension Cord 25 ft Power Cable with LED Light (NEMA 5-20P to NEMA 5-20R) - Amazon.com
Woods 20 ft. Multi-Outlet (3) Extension Cord with Power Tap, Green 859 - The Home Depot
20' Green Extension Cord, 16g wire | Holiday LEDS
Parkworld 67911 NEMA 6-20 Extension Cord 6-20P to 6-20R (T Blade Female Also for 6-15R Adapter) 250V, 20A, 5000W (50FT) - Walmart.com