There was an article in Creative Computing magazine in 1982 (PDF archived here) that showed you how to build an Asteroids layout button controller for your 2600.
Not bad...only took them 4 years after I did mine

I especially like how they got the layout completely wrong....

I so wanted to build one of those; I called up an arcade game supplier and asked if they had joysticks. "Not the kind you're looking for, kid" was the response, right before he hung up on me. 
Fortunately, the local amusement company owner was someone my dad had done some sign work for previously, and their businesses shared the same building at one point, so they knew each other. I spent a fair amount of time as a young kid wandering their warehouse and occasionally playing with their old pinball machines and parts (unbeknownst to them

). When I finally decided to try the real articles, we just drove over and took a walk through their shop. I walked out with a new WICO leaf stick and two Wico Leaf buttons for $10.00 (no room for an Asteroids layout on that panel, but I needed the extra button for the ColecoVision). I remember them actually being quite intrigued that such a thing was even possible, so they got a chuckle out of the idea and were quite helpful.