Mine usually come from Lidl or Aldi - I'm down to my last one and it's been sounding rough for a while now. It might theoretically be under warranty still as they tend to be 3 years from memory but given that I can't even remember which store it came from (it's lime green which I think would narrow it down) the chances of finding the receipt are slim.
It has briefly crossed my mind on occasion but they are usually slightly different from batch to batch and hey they're cheap enough and last long enough that they don't owe me anything by the time they do give up the ghost (well except the one my dad dropped from height that cracked they gearbox casing).So buy another when they are back on sale. Give it a few weeks then you have a receipt for refund.