The original Shellendrak *is* still available over on the Paizo.com website - along with several others which are also no longer available here on the main WWG website.
Caveats:
- it is at the old pricing structure of $22.99 (but then, it's the only place to get it)
- no updated kitbashes (if there ever were any) are available.
- the exterior ground tiles are 7x7 inches; but, the interior floors are 3x3, 3x6 & 6x6 sizes.
- the newer "West Wing" for Shellendrak, here, is in the TLX format - the older is a glue together similar to Mayhem Mega Mall, and not directly compatible with the TLX format.
You will find many older sets still listed on Paizo, but be aware they are all at the old price levels. Some listed there *are* available here on the company store site, but at the new lower pricing structure. So if you see something you need/want, double check whether you can get it here to make sure you don't pay more than you should.
[Can't help it, I'm hardwired as an archivist...
...and, yeah, I bought it!]** EDIT *** [couple weeks later...]
Also, important to buy an old set *here* instead of 'over there' so you can get any subsequent Kitbashes from it FREE !
Sounds unlikely, but, hey, things like the old Atlantis set got the TLX treatment!
Do I qualify for that? I didn't get access to it when I bought the sets through here. At least I think I didn't...