Eewwwwww....those are the obvious exceptions. Fortunately, they're also the least expensive pieces of equipment.
Very necessary though lol! My instructor bought metal ones back from Thailand that the MT fighters used, they are highly recommended if you can find them. Don't tie them up with the strings though slip them into a cup holder. One of our fighters tied the strings up very securely, lots of knots to make sure it wouldn't move during fight, problem is he couldn't get it off quick enough when he need to go the toilet rofl!
Can you tell I train in an all male club?
It's a pity we all live and train so far away from each other as a kit exhange/secondhand shop would have been brilliant. Some clubs/schools do run them though those that are out to make money insist you buy new from them.