You can use the Dr. Grip refill in the Acro Drive - $20 or you can go with a Rotring 600. Cannot say enough positive about the Rotring 600. Quality pen that takes Parker compatible refills. I use either the Schmidt EasyFlow 9000 or the Monteverde gel in mine. If you use CamelCamelCamel on Amazon you can get one for less than $30. I got mine for $24 a few weeks ago.