I carry a knife on each side. On the rare occasions on which I can legally carry a firearm (I'm not in the US) I drop one of the knives.
If you don't want a second knife, then perhaps something like an ASP baton.
Almost anything's better than fighting with your empty hands. I know what I'm talking about, I've been competing in muay thai and grappling for years, training seven days a week, coach my own team, and still consider unarmed combat as an almost insane SD option. We're tool using animals.
Whatever you chose, get a ton of realistic training. Make sure you understand your limitations and how things work (or don't!) under stress.
In fact, before you get a second knife I'd advice you to buy a training version of your Endura 4. So you can try out things like drawing and opening it while a couple of guys punch and grab you.
Stick and knife make a good combination. Even the shortest callapsible baton will give much longer reach than a regular knife, it allows you to block and might be better perceived by LEOs than a knife.
I'm not a fan of pepper spray. We've got our fair share of seasonal riots down here (the Third World is nice like that) and I've seen it fail too many times, even when deployed from the huge cans police use. It relies on the subjects pain threshold and some people can take a lot of pain and keep coming. It's better if combined with a baton or knife, but doing so might be illegal in some areas.
Whatever you pick, get a ton of training. Nothing dispels myths as fast as training. Avoid as many confrontations as you can, run away, talk your way out.