LTM CONCRETE Slab Bolster Chair 1.5 inch (12 Pack) – Heavy Duty Plastic Spacers, Supports All Rebar Sizes, Convenient 20 inch Length - Made in USA: Amazon.com: Tools & Home Improvement
Form Guard Slab Bolster – South Coast Steel Service, Inc.
PROWORX 3-in x 15-in x 3-in 25-Pack Steel Slab Bolster in the Rebar Chairs department at Lowes.com