you have two options, to lurk on Ebay and snag some rogue trader models when they pop-up (Like I do.)
Or
convert your own models, there is a tutorial on how
to make MK6 heads out of normal marine heads. After that get a glue gun with a fine tip and put small dots on the left shoulder pad.
Here is a picture of my 1989 "Librarian with Scroll"
P.S don't bid on anything I am biddinge on