I'm afraid it's not a normal DIN (or ISO) shape, in other words, it might be a Volkswagen special. DIN 609 ir DIN 610 is similar, but without the "toothed" part, also only goes till 10.9 Actually, that would be special, readily available is 8.8
If there's 8 bolts in the kit, and disassembling them from another 'box is gonna be hard work, I'd go for the kit tbh. It doesn't sound like it's going to be sensibly simple to find them from another source.
http://www.aseriesspares.co.uk/Fast...2-9-Self-Coloured-7/16-UNF-Sets/prod_599.html Price is for 10 bolts - various lengths available. http://www.aseriesspares.co.uk/Fast...ut-Hex-Zinc-Plated-UNF-Nut-Sets/prod_258.html Plain nuts, to suit - you'd need to use some thread or stud lock http://www.loctite.co.uk:80/cps/rde...redDotUID=productfinder&redDotUID=1000000IA39 Or use some all metal locking nuts: http://www.merlinmotorsport.co.uk/F.../p905/K-NUT-6-POINT-7/16UNF/product_info.html I'm not sure you'd want to use nylocs in the gearbox, as it's going to get hot in there.
long shot but ask your local seat dealer, most of the parts used are the same on vw's. part numbers are often the same, but price is alot cheaper.
Found a helpful chap in USA who will compare the specs to a similar kit thats cheap there and let me know and also found a guy who will part ex my kit if I provide what I need. Getting somewhere at least