Well when I was younger I had two primary interests outside of the team sports I played: history and video games. Fortunately for me sometime in the very early 2000's those two naturally lead me to take up an interest in older video games, and I decided I wanted an original Nintendo like the one I'd play that seemingly all my cousins owned when I was really little.
To do that I just guessed at a website domain name (in the days before decent search engines like Google or AskJeeves that's what a lot of us did lol) and landed on "usedgames.com"... I imagine over the following months that I directed my parents there for Christmas and my birthday and saved up money myself that we weren't actually getting a decent deal, but that collection I accrued actually came just before NES games began really skyrocketing in price. At this point I imagine they'd cost a silly amount more than they did at the time, so I'm happy that I took an early interest in them.
Actually, I guess that doesn't really qualify as a "bargain find" so much as it was just really good timing lol