Everbilt 3/8 in. x 1 in. Nylon Spacer 815118 - The Home Depot
3/8" OD Black Nylon Spacer Variety 200 Pack, 3/8" OD, 0.166" ID, 200 pack for VEX Robotics- Robosource.net
Crafted-Brand Heavy Duty Spacers – 1/2” OD, 1/2” Length, 1/4” ID for Screw Clearance, Unthreaded White Nylon 6/6, Never Rusts and Lighter Than Aluminum or Steel (Pack of 10 Spacers): Amazon.com: Industrial & Scientific