Where would I purchase micro-bore pipe for plumbing fridge freezer?

I bought a whirlpool american fridge freezer from curry,
the water pipe is only 2.3 metre long. I need an extension microbore pipe as my nearest water source is about 4 meter away. Is there such a kit or where would I be able to buy the pipe and fittings. I tried B&Q they don't stock any. Thanks for any tips