Unfortunately 6 weeks is not classed as a long term rental, this starts at 3 months.
Amoudara is about the only place within 5 kms of Heraklion that you will find plenty of accommodation. My advice would be to look on travel republic's site & book something for a couple of weeks. Then when you're here look for something else, or re-book.
You'll also find plenty of accommodation the other side of Heraklion in Kokkini Hani & Gouves, but that is around 12-14 kms of Heraklion.