Hello,
Did you post on this site for Precision sailboats by accident? The Pearson forum is just above on the list. Also, did you search for Pearson 26 with one of the search options like Google? Sometimes useful info like a manual or brochure will appear.
There was a man named Hammond in New England who traveled to boat shows like the ones held at St Michaels, MD. He had loads of info on old boats. At the time I purchased a brochure for a wooden powerboat he was charging $35 for an original in reasonable condition. I don't have any actual contact info for him.
Finally, eBay may give you a lead.
Best of Luck in your search. Phil