Yep ,, you can buy it at roofing supply companies like ABC Supply ,, just Google for the companies in your area. I bought some pretty good stuff for about 2 bucks a foot. The guys I used to put the gutters on a house I was working on wanted more to put the leaf guard pieces on than the actual gutters .
This is what I use for a parts and tool box working under hoods. I have bunches of magnetic trays, but with so many plastic fasteners they're frustrating. This style box, that cables come in, prevents stuff from falling out even if the box slides down the side of the engine. Or my favorite, between the the engine and radiator.
You never notice a missing valve stem cap when you're on your way to the parts department. It's always when a customer is waiting and it's lunch time. I solved that by sticking valve stem caps of various sizes on the allen screws on my lift motors. I've had one or two up there for a long time. The new ones will even nest, so I always have plenty right within reach.
I had to laugh yesterday when I was doing an oil change on a 1971 Chevelle. I took the oil cap off and dropped it into the hood latch like I always do. Young technicians were hovering around, looking at a car far older then themselves. One said "Wow, is it made to fit there?" I missed the opportunity to send them wandering around the car looking for the fuel cap. That would've really been entertaining.
I've had brass handled valve stem wrenches, black, orange and red plastic handles too. They all walk away from the tire machine or fall behind a tool box drawer. The economical solution is just a spare valve stem with a slotted tip secured with red Loctite. I snip the flange off square so it won't roll. Gets the job done without helping the tool man make a boat payment.