Swivel Snap Bolt
Ideally, your purse should be in your hand, over your arm, over your shoulder or across your body at all times. Across your body is the safest but, even there, pickpockets can slip a hand into your purse and remove your wallet without your noticing it.
Split Ring
You'll need two small items from the hardware store. One or two split rings, like those in key rings and one swivel snap bolt.
Hole in Zipper Tab
Feed swivel end of snap bolt into a split ring. Inside your purse, choose a compartment that closes with a zipper where you will keep your wallet and other valuables. Feed the slip ring through the hole in the zipper tab.
Strap Attachment Ring
When the zipper is closed, snap the bolt onto the ring that attaches the strap to your purse. If too short to reach, feed the second split ring onto the ring that attaches the strap and snap the bolt onto that. If the strap does not attach with a ring but is sewn to the purse, buy a large size split ring and feed the entire strap into the ring. Either snap the bolt onto this large ring or feed another small split ring onto the larger ring and snap the bolt onto that.
To be super safe, attach a second set to zipper tab on another compartment. Twist together before attaching to strap.