small wonder is on dvd or watch antenna or website online
I found that amazon has the first 2 seasons and www.ioffer.com has s3 and s4 for $55. on ioffer you have to register to get it.
if you want to just watch it antenna tv has it on sundays at 1 pm et or this site has all 4 seasons and its free http://watch-series.to/episode/small_wonder