Octopus supply a range of technical drawing pensn from Edding and Rotring amongst other makes. The Edding Profipen 1800 comes in 0.1, 0.3, 0.5 and 0.7mm lines as well as a wallet of 3 assorted wich contains 0.1, 0.3 and 0.5mm.
Rotring are famous for their technical drawing pens and have the Rapidograph and Isograph range. There is also the replacement nibs for the Rotring pens that are available separately.
Rotring also make a college set on both the Rapidograph and the Isograph ranges.