Lolita is one of the most popular fashion trends in Japan, and since it became trendy, there has been a lot of variations to the trend, such as sweet lolita, gothic lolita, classic lolita and even punk lolita, which were based on traditional Japanese and Chinese clothes but were altered to fit the Lolita standards.
With the popularity of the style come popular brands that specialize in the Lolita trend. Popular Lolita clothing brands are Baby, The Stars Shine Bright, Angelic Pretty, Moi-même-Moitié, h. Naoto and Metamorphose temps de fille. Notice that the brands are French-inspired, since the main inspiration for the trend is Victorian and Rococo-era clothing.
However, if you want to be more unique, you can just search the different surplus shops and mix and match the clothes that you find to create your own style.