Apple is now selling its Lightning to micro USB adapter on the US online Apple Store, and presumably in brick-and-mortar stores as well. The adapter plugs into your Lightning dock-enabled device (iPhone 5, new iPad or iPad mini) and then accepts a micro-USB plug. The unit will run you only US$19, and is currently set to ship out in one to three business days.
I'll tell you what Apple really needs to start selling: Lightning-enabled car adapters. I am still using my old (now offline) iPhone 4 to listen to podcasts in my car, just because my dock adapter isn't compatible with my iPhone 5's dock. Yes, I could go pick up a Lightning to 30-pin adapter (and honestly, that's probably what I'll end up doing). But I was hoping to use the upgrade as an excuse to get a brand new car audio solution, and none of those have yet appeared on Apple's website. There are still options out there, it just seems strange that this long after the iPhone 5's release, we still aren't seeing more Lightning accessories.