Look on aliexpress or alibaba and search for NC250 oil filter. You'll see both paper filter and metal screen filters. Some APJ who has a bike that uses the same NC250 engine as the RX3 comes with the metal filter. So if getting filters is difficult you could get a metal one. Wash it between oil changes and use it forever.
https://www.aliexpress.com/item/For-...ceBeautifyAB=0