Initially you should check you have a K2 roof, by using the information on this link:

You should then use the Search the K2 Directory area on the K2 website to be advised on companies in your area that can supply spare parts for our product, as K2 supply their products to trade companies only.

Gutter clips/brackets (Part No. C8043) are often listed on Ebay, though K2 will be unable to confirm a sellers identity or status for you, and you should use your own judgement.