I downloaded the demo of N.F. but can't find a place to purchase.
This is a discontinued application which means that purchasing is and won't be available in the near future. I've accessed the page and it redirects to a generic search page. Luckily, there are plenty applications already available as an alternative. Browse the link posted below to see a complete list with apps.
Sound recording lists (drag the slider to the left): http://software.informer.com/search/sound+recorder
If you don't want to search, you can use Audacity as an alternative: http://audacity.software.informer.com/