It is strange that over the centuries men have been trying to force their  unwanted attentions on Ladies.
In the Edwardian and Victorian days when the ladies wore slightly larger hats they needed Hatpins to stop their hats being blown away. This gave them a weapon to ward off unwelcome attentions (The Hatpin.).

If you research this item you will find that were quite long and very sharp, usually with an imitation jewel on one end.

Being stabbed in the thigh or hand or somewhere else would certainly cause the culprits to think of other things.

What would the ladies use these days?

Hats are out and also a hatpin might be classed as a concealed weapon.

What can they use?
A spray, you have to be careful of which type?

Perhaps a new style of Hairgrip suitable crafted would solve the problem?