To thicken up traces I'd use normal solid copper 1,5mm² or 2,5mm² house installation wire (NYM) with removed isolation.
Thinner wires like "round wire" are available but I don't have a order number (just some rolls of them in the bin - they last forever).
It's solid copper with silver coating.
The label says in German "Runddraht 1kg 0,2mm²"