Places for clothes in the 2000s :P

I recommend second hand stores like depop, ebay, vinted, poshmark and thrift/charity shops. Not only is it environmentally friendly but this is how you're going to be more likely to find authentic pieces instead of copies. Search by using old brand names for example, betsey johnson or juicy or use terms such as y2k, kawaii etc. 

you can find a ton of second-hand actual y2k clothes on eBay and depop but you have to be quick cause a lot of people will snatch it up so quickly you won't even have time to blink but it is absolutely worth it!