If you've ever lost a pin because the back fell off, these locking pin backs are your ultimate savior. Even if you want to get them off it's a pain in the ass, so you definitely don't have to worry about them falling off by mistake. I think this is what the army uses for their pins or something.
I'm not selling them directly because they're just so cheap at Amazon. Click above (or here) to get the pack that I bought for myself. It's 50 of them for a good price so you can protect your entire pin collection.
If it's just way more than you need, check the related products at the link above – there are smaller packs though the value isn't quite as good as getting 50 for this price!