Oversize pistons-kolben

Hello! My name is Grega Mlakar and I,m from Slovenia. Last year I have bought GPZ900r 1984 and I,m planning to completely rebuild him in original condition. But I have some problems with spare parts since here in Slovenia are not much GPZ owners. Now I,m looking for oversize pistons since mine cylinders has up to 0,04mm gap between cylinder and pistons. Could any one be so kind and please tell me where I could by a complete kit of four oversize pistons. I,m having some problems since I don’t speak German language. Thank you!