If Im reading this correctly, you need pure copper powder, from a solution of copper you've already managed to make? (If you havent, H2O2 + Vinegar + Copper will dissolve, slowly, and give copperacetate ions, which will work).
You do not need a strong reducing agent at all, any pure metals lower than copper in the reduction potential table will work, such as aluminium (as in tin-foil), zinc or magnesium.
The reaction is:
Cu
2+ + 2e
- Cu(s)
Al(s)
Al
3+ + 3e
-3Cu
2+(aq) + 2Al(s)
3Cu(s) + 2Al
3+(aq)
So all you need to do is make your solution of copper ions, the vinegar method will work nicely if you have time. If not, getting coppersulfate in saltform is pretty easy (ebay) and cheap. Then you just add aluminium directly into your mix.
This will reduce the copperions to elemental copper, in a pretty fine powdery form, and all you have to do is to filter it off. You might want to have a little excess copperions to make sure you dont end up with unreacted aluminium in the product though.