There's a new brand of full crampons called Katoolas (or something like that) that have short spikes and hinges for flexible shoes. Some hikers use them over trail runners. I believe they're aluminum and lightweight, which means they would wear down quickly if used on rocks or bare pavement very much. Might be a good choice for steep ice in the city.

When using any type of crampon, you need to learn kind of a bow-legged walk so your feet stay further apart than normal and you don't catch your points on your pant legs and trip. Gatiers are good for keeping the pants out of they way, but gaiter tears are still pretty common.