You might want to try this. It's kinda fun to experiment with. Here in the States there are certain green plastic flower pots that are rather ubiquitous. Some are brittle and you don't want those. You want the nice tough, flexible ones. Use an old guitar pick and trace out picks around the pot and cut them out with heavy shears. Trim them up and sand them to your satistfaction. They will be slightly curved and you can turn them one way for a soft stroke or the other for a stiff stoke or pick. I think they are better than any I've ever bought.

I've done the same with an old "Handicp Parking Placard". Similar but stouter stuff. Try different shapes and sizes. You can create the perfect pick and they last a long, long time.