Because I’m “German” and love wearing lederhosen, people ask me where to buy lederhosen pretty often.
In my personal experience, I’ve found Ludwig & Therese to be very good – providing good quality at a fair price. They’re certainly not cheap – the pair that I bought cost €110 – but they seem to be high-quality and reliable. They’ve endured a few Oktoberfests now.
If you get on their mailing list, you will get notified of their routine sales, typically in November and April.
In addition, other trusted friends have suggested these two places:
Generally, I suggest that you don’t buy the very cheap stuff off Amazon, unless you’re happy for it to shred the first time you wear it. If you just need a token pair of Lederhosen or a Dirndl for a one-off fancy dress, go for Amazon. Otherwise, spend a little more and get a pair that will endure.