Rays have Snow magic carpet sheets on clearance at $2.44 each
While the "Rules" say you can't use these inside resorts which is why they are so cheap I think they will make a great way of dragging gear over snow.
To counter the sideways slip issue any flat sheet has I am going to add small skegs at the back using 25mm aluminium angle.
My mates in the USA and Canada make proper winter sleds from this material up to 3 & 4 metres long
These are about 459mm * 1200mm long including the grab handles
I bought 4 sheets so a sled about 450mm * 3300 allowing for overlap if I make a long one but on its own just a handy size to drag a rucksack or a tub of firewood or shopping