Look, you shouldn't search for ugly sweater—you'll end up with one that's all obvious and funny about it. If the recipient knows you did it ironically, you've failed: the "prestige" moment is when they chuckle and say, "Haha! An ugly sweater!" and you respond with stone-faced silence. Just get one from this Etsy search; if they run low of good options, here's something at Amazon that's unlikely to sell out.