if you've got some digital calipers just measure the thread length to the hexagonal piece and the hexagonal piece to the tip of the nozzle and the internal diameter of the main bore.
And i'll compare that to mine :-)

Thanks for the offer - but if they're the same I'll just buy some myself :-)

these italian guys on ebay seem to do them and down to 0.2mm diameter as well dargonfly.
http://www.ebay.co.uk/itm/ESTRUSORE-...item4d2274ba47

But they want £6 postage for something that might weigh 5 grams.
You could probably tape it to a postcard and it'd get here.

I think I'm either a mk7 or mk8 extruder. Probably a mk7 looking at the ebay adverts for the machines.
I have no idea what the difference is or how you tell which is which.