Found a useful site here that lists all the places you can either get an Antigen or PCR test throughout Taiwan for travel to the US.
入境美國COVID19陰性證明規定取消；台灣自費抗原快篩醫院清單整理
Site is in Chinese but addresses for clinics and hospitals by city/district are at the bottom. They provide the fee and whether they do PCR (核酸) or Antigen (抗原）