kz440 cylinderhead washers

I noticed my kz440 dont have the copper washers for cylinder head.. can I use steel washers or do I need to find some copper ones? I dont really want to order originals online because I would like to be driving already, this is why I am considering steel ones.

Steel ones may leak. The purpose of using copper is that it is a soft enough metal to conform to the little irregularities of the head and nut well enough to prevent an oil leak. That is why the oil drain plug has one, too. Any decent hardware store should stock them. I suppose in a pinch, soft aluminum washers could work.