The Blue zirconium discs from ebay are as good as any I have tried from my local welding supplier, but you normally need to buy a hundred to get them for anywhere close to a pound each.
There are plenty sold at car boot sales and probably ebay that last about a minute each, you can see by looking at them that the quality is poor.
A pack of 10 Kingspoor or similar from my local welding supplier worked out around £2.20 each last time I enquired
£11 each is outrageous.
if you email me your address I'll send you a couple of the blue ebay ones to try, me and a pal buy them by the hundred and have 50 each.
Alan.