http://h20000.www2.hp.com/bizsupport...pp01068#N104EA
You can order them from HP there.  I can't seem to find that manual online, but you may want to take a look yourself.  They have online manuals for most of their printers and scanners... what exactly IS the draftmaster, anyway?  I can't seem to find it for sale on the site, either 
 
There's this site... which seems to have some sort of manual for a Draftmaster P (plus?) 60 and 160.  Maybe that will help... 
http://www.bratlady.com/HI_plotter.shtml
I can't seem to find much else.  I hope that helps a little bit.