Try chamfering the pencil then dip the end in rubbing alcohol... it should slide in, maybe will need some elbow grease and cuss words. The alcohol acts as a lubricant and then evaporates. The cuss words just make you feel better.
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I second the suggestion on the Pilot Croquis by Imla, above.
As for attaching it, see http://www.scubaboard.com/forums/accessories/333263-putting-leash-pilot-croquis-pencil.html