Hmmmm......gota watch the forklift driverssorry, no help, but heres a good sticker to add to the mix
http://www.labellab.com/Safety-Banners/Forklift-Drivers-Do-It-Low-and-Slow/SKU-B-0038-3x10.aspx
Do you know what brand of lift truck it is? They look like manufacturer supplied graphics.
Sorry if you've already thought of this, but maybe a call to the manufacturer or distributor of the lift may get you there.
SP