You're not going to find any more new TDSE's using that PN... or any other PN for that matter.
When I was working on retro-fitting the VIP system to work with my 89 (and had it narrowed down to just a couple of wires), I emailed fujitsu-ten to see if anyone would be willing to help me out.
I was shocked to actually get a response back from them but even more floored when I read the email.
They had about a dozen full TDSE kits sitting in their dead parts bin. The reason most dealers couldn't find them was because they changed the part number. They gave me the new part number and I made a few phone calls. Jeff Watson immediately ordered every last kit - he had a waiting list for these things. I got mine from that batch and then we posted up on the Supras.com mailing list (before any of the forums were even around) and the remaining kits were sold in less than a week.
You're best bet is to scour ebay etc for used ones.
IF I ever decide to sell my Supra I'll be taking the TDSE out and putting it up for sale sep. But since I don't ever see that happening...
The TDSE adds remote keyless entry and a glassbreak sensor. It also has a switch to turn off the horn during arming/disarming.
Keith