Just found this “Plastic Fountain Pen” by Craft Design Technology and Pentel... it has a very interesting nib & cartridge system. Have you ever heard of these? : r/fountainpens
School Supplies Pens | Fountain Pen Pentel | Fountain Pen Refill | Pentel Tradio Pen - Gel Pens - Aliexpress
Amazon.com: Pentel Stylo Fountain Pen - Blue (Pack of 12) : Everything Else