These products are currently only available in physical stores at Universal Studios Japan. However, you may be able to find some resellers on https://buyee.jp/ . Please see Shop General Merch Sources > Secondhand Merch Sources for more.
Address: 2 Chome-1-33 Sakurajima, Konohana Ward, Osaka, 554-0031, Japan
Phone Number: +81 570-200-606