Please could you provide a little more information about your matrix which you are analysing? and please define "simple", Ion Chromatography will do it but is this too complex or is it unavailable where you are? do you want a fast colourmetic test?
Is it a solution or solid? is it a mixture, what copper salt is it? Are you trying to quantify exactly how much Cu(I) you have in the presence of anything else? if so what else is present?
There are a few methods which you could use but the questions above need to be addressed so that you can find the most applicable to your needs.