eBay and Craigslist finds

Magic gears are more likely to have chain issues.. in my case a lack of chain tension on my ss caused chain slippage on hard take-offs a few times before I had the sense to add a tensioner. Some people run magic gears fine but it will depend on the gear, the chainstay length and the design of the dropouts..

get old and large sprokets/chain rings and squeeze them inbetween the top and bottom bit of the chain...