Look up mildliners (for ex ZEBRA MILDLINER Highlighter pen markers, Mild Gray (WKT7-MGR) x 10 https://www.amazon.com/dp/B07FZJ6D19/ref=cm_sw_r_cp_api_i_uGGyFbMEJ4M3S)
Look up mildliners like these ZEBRA MILDLINER Highlighter pen markers, Mild Gray (WKT7-MGR) x 10 https://www.amazon.com/dp/B07FZJ6D19/ref=cm_sw_r_cp_api_i_uGGyFbMEJ4M3S