You can plastic Ion bolts from
www.luckyeurope.co.uk.
Its called the stage 1 V3. Its also has better flow characteristics than any other ion bolt, and it seals the firing chamber on the forward stroke more effectively, for better efficiency.
But the stage 1 isnt delrin its a different crazy plastic composite. When Delrin is sitting in grease for a long time it can swell inside your marker which isnt good.