The mk1 is meant to be better as it has a metal bit at connects to the camera (I know there is a proper word for it, my mind has gone blank though) and the mk2 is plastic.
Kerso is usually a god bet for lenses, if nt Warehouse express or check camera price buster...

Warehouse express is over priced for this particular product. Not sure where to get Mk1's but for Mk2's:
Kerso has them on eBay for £65inc, they are also on Amazon for £65.38: http://www.amazon.co.uk/exec/obidos/ASIN/B00005K47X
Cheapest I've seen them so far is wbessada @ £59inc, he is a trader on the forums but I think he has run out atm. Best to PM him.
Looking myself as it happens!![]()
You will get them a bit cheaper from Kerso if you email him & mention TP!
Spence