Hi Paul you might be struggling to get the bits in a hurry for the weekend unless you end up paying top dollar locally somewhere. Blades you might be able to get from the ODK store (postage time will be the problem) and the same with these from ebay Melbourne supplier.
/www.ebay.com.au/itm/Victa-22-30-Inch-4-Blade-Kit-Suit-Super-24-600-Slashers/302679211940?
These blades being longer give you the cutting width you need using the 18 inch carrier. I will see what carriers are out there I should have some round ones here but again you won't be cutting the grass this weekend
This is the type of blade carrier you want but this one is no good because the blade bolt hole at the top has been flogged out so you can only fit 2 blades on this carrier
www.ebay.com.au/itm/Genuine-Victa-Blade-Carrier-Disc-Quad-Disc-Blades/302422351257?This is a better option and it is new
/www.ebay.com.au/itm/Victa-GENUINE-lawnmower-cutting-disc-Blade-carrier-FITS-BOTH-18-AND-19-de/292757874632?
