Ebay offers Greenworks 15" Pressure Washer Surface Cleaner Attachment for $36 (reg $80) with free shipping.

Product Description:
Clean even larger areas faster and more efficiently with the powerful 15" Rotating Surface Cleaner from Greenworks. The quick-connect feature makes for easy setup and the dual-nozzle cleaning head will power through all of your driveway, floor, patio, deck and sidewalk cleaning needs! Dual-nozzle cleaning head makes short work of cleaning floors, driveways, patios and decks. Larger diameter 15" cleaning width allows you to clean even the largest areas quickly and efficiently. Quick-connect feature allows you to easily connect/disconnect from your pressure washer wand. Durable poly-housing and brush water guard helps contain the cleaning action. Universal fit with most pressure washers up to 3100 PSI!

• Dual-nozzle cleaning head
• Universal fit with most pressure washers up to 3100 PSI
• Diameter
• 15" cleaning width
• Quick-connect feature
• Easily connect to compatible models