Quit screwing around and install a front brake.

Even if you have 2 brakes, the front brake does 80% of your braking.

You can buy a fancier lever later for your new handlebars, but get a regular front brake and brake lever and install them ASAP.

You don't always have the luxury of avoiding traffic, and when you need to stop quickly, there isn't a substitute for a brake.

It's a lot cheaper than a trip to the emergency room.