I have a pain in the ball of my foot. What OTC insoles will help?

Forefoot pain. There are so many potential problems that this is hard to answer. It can be related to bone, soft tissue, nerve and blood flow.
Root of Foot Pain. OTC insoles are a good start, but it's important to find out what's causing the pain. It could be nerve, bone, joint, muscle, ligament, tendon, skin, stress and strain, or any combination of these. If the pain persists, see a podiatrist.
Remember . You are better served by first determining the cause of your pain as just randomly using any old insole/insert may actually make the problem worse. It sounds like you have metatarsalgia, which can be caused by problems with the bones, nerves and/or the soft tissues in that area. If you really don't want to seek help you could try a Pro-Tec metatarsal pad.
Save your money. Most common otc insoles aren't as good as you would like them to be. To make them inexpensive, they're typically made of inferior materials. In addition, you need to find out why the ball of your foot hurts. Merely cushioning them, especially with flimsy insoles, won't provide all that much help.