Hi Eleanor, I can recommend Stablecroft Conference Products for badge trays.
I have their metal ones which I bought about 15 years ago and still look new, which is pretty sustainable- but heavy.
This year I bought some cardboard ones which are v light and have matching exact sized boxes, so you can get them all ready in UK and send to Zurich.
When I first used them, they also ran a donkey sanctuary charity alongside the business but I can’t find anything on their website about it now. I am sure I didn’t dream it though, they used to send me emails about what donkeys they had rescued.
Hope this is helpful.