If you buy a pendulum you like, you can easily remove it with pliers, leaving the first large hoop and slip it onto a chain or cord to wear around your neck. Be sure it is a smaller pendulum. Some can be quite heavy and would break around your neck or just plainly be uncomfortable and bulky. Also most crystal point or gemstone sphere pendants can be used. Remember, the first pendulums were a rock on a string. I've also used a ring on a strand of hair. That's when you really come unprepared! LOL The possibilities are virtually endless.
Not everything works well, some just move better than others, and generally differently depending on the people that use them. I had a pendulum that I hated because it would barely move. I said it was "shy". I gave it to my husband (boyfriend then) it swung like mad for him! And my favorite one, that is smaller and lighter, barely moves for him. .
Instead of saying "this is yes, and this is no", I suggest asking "yes?" "no?" and see how it swings.