eBay - his shop can be viewed here. http://stores.ebay.co.uk/Civic-Technologies I've found them to be very good. P.s watch your fingers with neodymium magnets, i've pinched skin more times than I care to remember - super strong.
You can also get neo mags from Hard disks. They have to be broken in half as they have two poles but are a good cheap(free) solution. You can call computer repair shops to ask about broken hard drives.