I think you can only get the SPU 90th as an NOS aftermarket purchase, which means without the normal Ortofon warranty. Take a look on eBay. 2juki often sells them. I've bought from him before and he's been dependable.
The top of the current SPU lineup is the Royal GM II. I have one, along with an A90. They both have the Replicant 100 stylus, which makes them a little more closely related, but they still occupy different genres, as others have said. I really enjoy the Royal's unusual combination of SPU-like body and coherency plus excellent detail and sparkle on top, for which most SPUs are not usually noted. Still, the A90 is the better all-around cartridge for soundstage depth and layering, imaging, and the other audiophile characteristics while still being IMO very musical. It is extremely sensitive to all set-up parameters, however, especially VTA, so I don't think the Schick is the best arm for it. The Royal is much less finicky though it still wants VTA changes for different record widths. The SPU 90th, without the Replicant, might be less demanding in this regard, I don't know.
The top of the current SPU lineup is the Royal GM II. I have one, along with an A90. They both have the Replicant 100 stylus, which makes them a little more closely related, but they still occupy different genres, as others have said. I really enjoy the Royal's unusual combination of SPU-like body and coherency plus excellent detail and sparkle on top, for which most SPUs are not usually noted. Still, the A90 is the better all-around cartridge for soundstage depth and layering, imaging, and the other audiophile characteristics while still being IMO very musical. It is extremely sensitive to all set-up parameters, however, especially VTA, so I don't think the Schick is the best arm for it. The Royal is much less finicky though it still wants VTA changes for different record widths. The SPU 90th, without the Replicant, might be less demanding in this regard, I don't know.