The idea for a double tip pen came from the user Jugglervr (thingiverse), so if you like it, make sure you thank him/her aswell.
I was hoping he/she'd post a remake him/herself for full creditibility but I understand the struggle of modifiying STLs and comitting time to it. So I went ahead and quickly modified the cad files because I believe it was a very interesting and useful idea.
You need to download the tips and tip caps from the main thing page as I only added the pen bodies here.
It is a hard print considering the initial surface area and you do need a bit of support at the beggining, specially the 5mm non reinforced version where the base is a single line.
I advise to print it with a brim if you are not 100% confident on your adhesion and carefully debour the print afterwards.
The tip storing feature is gone, naturally, so I went ahead and made the whole body with the same inner diameter (still enough for 10mm and 5mm strips (3-4mm reinforced version))
The author remixed this model.