the best ting about having CASA define a type of shoe, is that it is now a required piece of aviation equipment, ergo tax deductable. Every year, there would be a cliam from me for "non sparking shoes". It has been in the regs for many a year! at LEAST 18 years.
As to what are non sparking shoes? I think that as long as you don't wear tap dancing shoes, then you should be OK.