Where to find the most difficult puzzles possible?

Hello, My mom loves puzzles and every year I get her a couple for Christmas. The problem is, they are always too easy. We've gotten ones that are repetitive patterns or all the same colours so the picture is difficult, and the largest we've found is 2000 pieces. I'm fairly new to Ottawa area so I'm hoping there's more options here. So puzzle fanatics, where do I find the most difficult, highest number of pieces possible? If there are any unique ideas please share those as well! Thanks!