Nuc Entrance Disc/Hive Portal - where to buy?

Hi all just starting to think about building traps and Nucs over winter. I was wanting to try an entrance disc/hive portal like the betterbee ones http://www.betterbee.com/beemax-hive-equipment/bhp1-betterbee-hive-portal.asp but can’t find where to buy in (Western) Australia or online. Looking for discs around 200mm/7"

Any suggestions or alternatives?

Adam

Make sure your disks do not protrude past any edge of the box, bottom, sides, or top. That would mean your entrance needs to be just over 3.5" above the hive bottom.