Its definitely harder and harder to find some stuff for older Toyotas at local dealers and local parts houses. I've all but given up on them and source my stuff almost entirely online. For drivetrain parts, lots of it can cross-over to other Toyota trucks and Cruisers, so I'll check with my homies at Cruiser Outfitters (
www.cruiserteq.com and
www.cruiseroutfitters.com) and see if they stock it or can get it. But pretty much everything else, I go straight to searching online. I haven't run into too many parts that I've had an issue finding for my 1G Tacomas and 3G 4Runners over the years (other than the brass rings that go on the hub bodies for the manual hubs--but those were never available separate from the hub body from Toyota anyway) and I have bought a lot of parts over the years. Anything for the 1st Gen Tacoma that crosses over to the 4Runner/Hilux Surf usually is readily available overseas too if you cant find it in North America.
I have seen where folks were saying some of the interior parts were getting harder to find new. Oh, and of course, the older remote entry/alarm systems have basically been unobtanium for ~10 years now (back in 2013, I sourced the very last remote entry system ECU in the country for my 2001 Tacoma DCSB (at least thats what the Shaman told me at the time

))
But ya, it sometimes takes a good bit of effort to track down part numbers for some of this stuff. I'm no part number guru like CruiserDan or Beno... but I've been tracking down parts for Cruisers and Toyota 4x4s for quite a few years now (even got kinda paid for doing it for a bit at one point) ... lol But I seriously love combing through the parts diagrams looking for part numbers for cool OEM option stuff that I need to add to my trucks.