I don't know if it was different for 2018, but my 2019 came with the
Mobile Connector with both NEMA 14-50 and NEMA 5-15 plugs, as well as the
J1772 adapter. The latter might or might not have been stored with the former in your boss's car. Tesla's site shows the former as being out of stock and reports it will begin shipping in August. If you need immediate replacement, then you might be able to find something used or from a "third-party seller" (scalper); or you could go with a similar portable level 2 J1772 EVSE. There are lots available, but be sure to go with a reputable brand, not a fly-by-night Amazon/eBay "special" from some unknown Chinese manufacturer.
A side note: Tesla's site is currently showing just one Mobile Connector, with an option for either NEMA 5-15 (120v; level 1) or NEMA 5-15 plus 14-50 plugs (240v; level 2). I seem to recall that when they first dropped this item as standard with cars, they announced two Mobile Connector offerings, one of which was level 1 only and the other of which supported both speeds, with a big price gap between them ($200 vs. $450, IIRC). I don't know if my memory is faulty, if Tesla rapidly changed their product lineup, or if the current Web store listing is incomplete/inaccurate.