We want to generate a spark suitable for igniting a potato cannon (alchohol class fuel) preferably without automobile-class coils
Get a propane gas BBQ Grill Ignitor.  There are electronic versions, as well as piezo-versions that don't need batteries.  You can buy them at most big box hardware stores like Home Depot or Lowes.  

Something like this:  http://amzn.com/B000FJLMOE