pst2
 

not mine ...

Diagnostique PST2 Porsche 911 964 993 996 986 Boxster Cayenne GT1 GT2 GT3 968 | eBay

Here is a PIWIS on Ebay

Piwis 1 V34 Diagnostic System Based on Bosch KTS 650 | eBay

PIWIS I is already way out of date, PIWIS III is current.

But wouldn't the PIWIS still be useful for home/small group/small shop use?

Depends; these things are perpetually being updated with new diagnostic information and access the TSI data bases. When the PIWIS I was superseded by the II (and now III), Porsche purposely cut the I's off from any updates or TSI access, somewhat limiting their usefulness. It also cuts it off from any of the later model year cars.