First, I ordered this massive 48L top case from Amazon. $52.88? That's barely $1 a liter! Cheaper than Coca-Cola!
Upon arrival, I noted that the light panels were removable so I outfitted them with a set of combination rear/brake/turn LED strips. $6.95 shipped:
These turned out to be housed in a rubberized container which wouldn't fit within the top case light area, so I de-housed the strips and mounted them in the top case with double-sided tape. the red housing covers the area nicely with no gaps for water to get in, however I will fashion a bit of silicone sealant as well.
I wanted the top case to be removable, so I then built a wiring harness for the top case lights utilizing a 5-wire waterproof connector from here, $4.30:
This gave me the ability to remove the top case in about 30 seconds with the single hand-tightened bolt (pictured), and tuck the wiring harness under the seat area or behind the rear bracket.
Finally, an $8.45 knock-off Vespa logo for my knock-off Vespa case: https://www.ebay.com/itm/3D-Silver-Color-Vespa-All-Models-Front-Badge-Sticker-4-Inch-Like-656219-NO-OEM/202345462832?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
The top case attached with no real drama, so I won't bother with the write-up for that part. I did have to get some longer bolts to utilize the holes built into the rear rack, but that was optional.
Results posted below. Not too horrible! Pretty stable! Very light! And for a shade under $73 (labor, 18ga wiring laying around, solder, shrinkwrap not included), I'll take it. To-do includes some conduit for the wiring, and a flasher for the brake light.