Thought I would respond 7 years later
He is my uncle and is still alive and lives in Cape Cod, he has to be around 87.

Hello,

i happen to be an ever so minor acquaintance of Mr. O'Sullivan and i thought of him yesterday as i serendipitously met him in a local CVS.
i am a writer and illustrator (see http://ckk.name if you wish) and hope to have my next illustrated book out by this time next year.
i live on the Upper West Side of Gotham (Manhattan .
Until recently (my Radar is in Heaven now) my 'roommate' was a scrumptious Lab (and likely LabraDane), Radar, see http://ckk-ink.com/21101.html if you wish. I put Radar in my pocket when he was perhaps ~ 5 weeks old and he graced my life with JOY for ~ almost 12 too too short years.
He had diabetes and even had miracle sight saving cataract removal / lens replacement surgery performed by the Wizards at Cornell Veterinary College ~ 5 years ago. We were for all intents and purposes inseparable. Radar was a scrumptious, smart and sweet rascal who had many, many friends, was a gentle giant and was often called 'gorgeous' as we walked down the street (of course, i thought people were speaking about me, but they always corrected me if i were to ask 'what about him' . We had different constitutionals (paths), including but not limited to Central Park (often its Great Lawn's environs), Riverside Park and others ... When Radar had his surgery a handful of years back, we'd often spend our time together after i'd hose him down in the local Riverside Park 'dog run' sitting on the dog friendly, shaded grass or when appropriate on a park bench in the shade just north of the Soldiers' and Sailors' Monument and people watch ... we'd meet many people and as i'm gregarious when i'm in my comfort zone (when i was with R, i was usually, if not always [ok, when it was 7 degrees, snowing/sleeting sideways and i was a bit under dressed or wore the wrong, not quite water proof shoes!! i may not have been in my comfort zone]) in that comfort zone) ... i'd meet and chat with many people while we strolled or sat and watched people go by ... i may include fictionalized versions of some of these tales in my next book, in a chapter possibly titled The Radar Report. ... one day either Tom was sitting in 'our' (Radar and My') spot or we were sitting in Tom's spot in the shade on a bench on Riverside Drive ... when i showed him my book and told him about my work and future goals, he told me about his career and provided wise counsel. At the time i was (when time allowed) attending the sketch classes at the Society of Illustrators ... http://www.societyillustrators.org/Events_Programs.aspx?id=1380 ... i attempted to interact with the curators at the SI, as Tom is slowing down, his vision is not the best, and i personally think it would be appropriate to have a valedictory type festschrift / show of his works @ the SI in New York ... he has certainly had a prolific career, he's a nice fellow and deserves such goodness in his twilight time(s). Bumping into Tom yesterday, resurrected my interest in such an endeavor and googling led me to this string / query. cheers/all the best. http://ckk.name. I hope this helps.

I too am interested in buying Tom O'Sullivan prints! I went to the web address, listed earlier in this thread by his nephew, but it doesn't appear to be an active site any longer. When I read that he had original illustrations from The Cat Who Stamped His Feet, my heart skipped a beat as this is one of my favorite books from childhood that I've held onto.

Thanks in advance for any pointers!