Ribbon Laser Bonding on PCB

[Kneidl]

Hi, I am working on a project where we need multiple ribbon bonds attached to a PCB using laser welding.
The downside of the technology is that according to the machine manufacturer, the copper-tickness on the PCB-side must be at least 400µm.
As I would like to avoid any special PCB manufacturing process like copper-inlays, my idea was to just solder some tiny pieces/plates of copper or nickel on the top side and then the laser can weld to them.
But I cannot find something like a reeled 5x5mm (max. 15x7mm) copper plate on digikey, or at least I don't know in which part category I have to look for.
The closest thing I found to what I need are some shunt resistors (digikey: BVE-Z-R0001-1.0) , but the low resistive ones are too big or have a non flat surface and are in general kind of expensive.
Can someone tell me to what I should look for or maybe has a better idea to a rather cheap and mass manufacturable solution?
Thanks