I'm in the U.S., but I have an idea. Find a source for sheet brass and make your own. Here one can get what is called "shim stock", brass sheets in particular thicknesses. I remember 0.010" (ten thousands of an inch) being common. I'm sure you would need a greater thickness for a plectrum. The brass is easy to cut with sheet metal shears and probably even with ordinary household scissors. It can also be easily flattened (it tends to curl when cut) and the edges can be filed/sanded down to make them smooth. Check at an automotive machine shop or similar place to find out where to purchase the shim stock.

I actually own one or two brass plectrums. I believe I bought them at a music shop years ago. I don't recall seeing any in stores for the last several years.