If you want non-metal poles, there are carbon fiber poles available. I've used the MSR Overland Carbon, and like them. I believe there are also some sold at Gossamer Gear and/or the BackpackingLight websites.

Of course, I've also used sawed-off broom handles and the "utility" handles (replacement handles for rakes, shovels, etc.) that you can find at hardware stores. My son once made a nice hiking pole out of a fallen tree limb he found.

You mention you're only walking city streets now. Does your city have any local parks that might have a walking trail? Mine has a track laid around the local soccer fields. It's about a mile and a half long; probably half a mile is beside a creek, under some trees, and all in all it's pleasant enough. I try to get out there about 2 or 3 times a week and walk a couple or three laps. I carry my pack, packed for a weekend, and use my hiking poles. One thing that was jarring was that, on backcountry trails, you speak to anyone you meet and they usually talk back. On this trail, you can smile and speak - and get ignored. Must be something about cities (my "city" is 10,000 people in rural Ohio - and prides itself on its small-town friendliness!)