Another more likely source of the creak is the sintered bronze bush which is installed in the top of the pedal assemble, if you ignore this it will wear the cross shaft and then you have to find one of those.
About Time Spares have thses bush's NOS and reasonable priced, I recently replaced both of mine and it makes a huge difference to the pedal movement, they have to be prelubricated before installation as per the workshop manual.
http://www.abouttimespares.com.au/They are not too bad to replace the hardest part was getting the individual pedals out, I have a heater demister installed in the way,if it was not there it would be a piece of the proverbal (About 2 hours from start to finish with the heater in the way). Oh I do have a bench press which made it easier to push in and out.
Good Luck
John M
PS WD40 is a very short term fix as it actually wash's the grease out of the bush.