The Schwalbe Marathon Winter is a studded tyre that will allow you to stay upright on ice, provided you ride reasonably carefully. On snow, it's no more than average. It's designed to be run all winter, and isn't too slow compared with summer tyres of an equivalent size & tread.
Studded tyres with big knobbles for snow are also available from Schwalbe & Nokian, but they are slow, and bigger than 38mm. Continental studded tyres use steel studs that wear when used on road.
Another option is the Continental Top Contact Winter II. This isn't studded, but uses a special rubber compound and tread design that gives good grip on cold ice or compacted snow, like winter car tyres (probably not so good if the ice is melting).
Winter tyres are generally best looked for on German websites such as bike-discount.de, starbike.com or rosebikes.co.uk. Don't forget to include shipping when comparing prices.