Purdy Revolution 18-in Plastic Standard Paint Roller Frame in the Paint Roller Frames department at Lowes.com
Amazon.com: ROLLINGDOG 18 Inch Paint Roller Frame - Adjustable from 12" to 18" for Large Area, Ceiling, Floor, Wall Painting, Can be Attached to Threaded End Extension Poles : Tools & Home Improvement
GRACO 24W128 Spray Roller,22 in. L,12 to 18in Roller: Amazon.com: Tools & Home Improvement