I tried a 2 hour snowboarding lesson once and gave up half way through. This was because I caught an edge and landed on my coccyx and was in considerable pain. I've never been near a snowboard again as I never want to repeat that experience. If I'd had impact shorts it could have been a different story. So my advise would be find some impact shorts as its unlikely anyone will want to share these! As I think someone has already said, Lidl and Aldi will be due their Winter Sports items soon - you can subscribe to Lidl to get the advance notice of what their offers will be for the following week.
Otherwise, check out the EF Market Place for 2nd hand goods.
If you don't take up snowboarding, you can always sell them on again - although maybe not the impact shorts!