Ordered from SIP but it didn't fit my folding rear rack. I guess it only fits Vespa fixed racks. $50 and free shipping. See my Ebay posting.

https://www.ebay.com/itm/Vespa-Top-Case-Holding-Plate-for-LX-LXV-S-50-150-PN-PI622183/263694463591?epid=25019499829&hash=item3d656a3267:g:~SwAAOSwPDda~XyQ[url]