I have managed to lose the blue card which indicates the time you park in a blue zone, can someone tell me where I get a replacement please

any police station or stva office post office also i think

You can also buy them in most service stations and any Co-op Brico and Migros do-it.

Normal Migros & CoOp's as well.
Also any parking attendant, I was kindly left one with a parking ticket a couple of years ago as I was still using an old style one!

Best place is to go to the police - where you can pick up one for free

I recently picked up the cardboard style for free at the Gemeindehaus where I was helping a client register. They also had some at the bakery in my village. It seems I have always seen the cardboard ones for free but I did buy one that sticks to the front windscreen which is very convenient (you can remove it and reapply it over and over). I bought it at a gas station.

Aw bless... ain't they helpful, but this is what I want to avoid so I'm of to the gemiender, thanks all

assume you are also trying to avoid the police station