What are you specifically looking for on the inside? Dash assemblies were shared among all full-sized '61 Olds, so if you're searching for bezels & such you may find what you're looking for on Ebay if you're patient. Speedometer bezels are especially prone to pitting-if you're looking for one of these you may well have to bite the bullet & pay to have it repaired & replated.
Are your armrest bases cracked? Replacements turn up on Ebay fairly often. They invariably need to have the chrome redone, so if yours just need replating, you may as well keep what you have. I had a set replated here:
http://www.vacuumplaters.com/ They did a fine job, it was fast, & relatively inexpensive- around $50-100 for 4 pieces.
Bumpers, hood, & trunk are also shared among all '61 Olds full size. Doors are identical between all '61 & '62 88-98 coupes & convertibles. Ames Pontiac carries inner lower door panels for these. Otherwise you're probably looking at hitting up some of those West coast metal places.
Non-mechanical aftermarket support for this car is almost non-existent.
The rear trim panel was used only by the Starfire & the Ninety Eight. These are very hard to find in any condition. On my Starfire, this panel ultimately wound up being painted argent silver, then the pot metal appliques were bonded on after replating.
Side trim is exclusive to the Ninety Eight Holiday Coupe & convertible. You're talking about a total run of 4445 coupes & 3804 convertibles. That's not a lot. There are six very long, thin stainless pieces on each side of the car, for a total of twelve. Very often the body between these pieces was painted a contrasting color- you could determine that by posting the paint code off the cowl tag. Anyway, these are super-scarce. It is very easily damaged if removed improperly. If you still have the trim, regardless of condition, you're probably looking at having it refurbished by one of those stainless places. I've been searching for a full set for over a year with no luck.
There was a slack-jawed fool on Ebay a few months ago who was dumping his aborted '61 Olds 98 coupe resto-rod disaster (I guess after he thoroughly f***ed-up the car he realized it was too hard to keep it running...) The trim had been shaved, so I contacted the guy to see if he still had it.... he had thrown it away.
I at least enjoyed telling him that he could have named his price on that trim...
Please post a few pics of the car you're working on- I'd sure enjoy seeing it.
Chuck