you should be able to get some off ebay via HongKong, I have some on my bikes and can't fault them and under £20 inc. p&p.
You can't adjust the clutch too much as you need the movement to opperate the clutch? make sure the cable is oiled you can make a funnel from a small plastic bag make a hole in the corner just big enough to get the cable through then tape it to the outer, put some oil in the bag and hang it up for a few hours or until it comes out the other end, it makes the clutch much lighter to use.