I like this one from OEM Tools. Although it's now like four times what I paid for mine several years ago. Soft fleece, removable magnets, washable.
OEMTOOLS 24899 Soft Fleece Fender Cover
www.mobiledistributorsupply.com
Second favorite would the cloth ones provided by uniform companies. Soft, easily secured to car with binder clips.
Cheapest option, buy a few of those Harbor Freight moving blankets when they're on sale. Wash them a few times to soften them up. At about $4 a blanket makes them almost disposable.
Personally, I try not to place tools in an open engine compartment to prevent loss, damage, accidents. A small two shelf cart I roll close to where I'm working it where the tools in use, parts removed, and new parts hang out. Good luck in your quest
