Here in the USA, the only level 3 adapter available for Tesla is the CHAdeMO adapter. However, this is limited to the old standard of 50KW. Originally CHAdeMO was limited to 62.5KW per the international standard itself, and thus charging stations would standardize at 50KW for CHAdeMO and CCS (Combined Charging System or SAE CCS1 in the USA).
However, the CHAdeMO standard was revised to version 2 (aka CHAdeMO 2.0), which in theory supports up to 400KW (higher than any current Tesla Super Charger). Because of this update third party companies such as Charge Point are not building out 250KW (the same speed as the fastest Super Chargers).
Now don't get me wrong, the Super Chargers are great. No need for a separate account or calling up to pay with a credit card. The button on the handle to pop open the charging port or stop charging instead of needing to use the cars touch screen or app is a welcome convenience. Not to mention not needing to use an adapter is so much easier.
But the Super Chargers are as available as other chargers in various regions. Most third parties are regional, though expanding nationally. But because of the regional focus they have a lot more charging stations in a single area than Tesla. Here in the Boston area, we have a couple options in downtown Boston with gen 1 (72KW) Super Chargers (not much faster than 50KW which have a lot more locations in the city, though they are still noticeably faster). Outside the City there are a few Gen 2 (150KW, formerly 120KW, but are really closer to 148, but only if no one else is using the other charger in the pair). I am not aware of any Gen 3 Super Chargers even planned for the area. I see these more being in Connecticut rest areas than in Massachusetts. Especially since most of the Super Chargers in eastern Massachusetts are at Tesla Stores, or some like the one in Mansfield, MA are a little further off the highway than I would normally want to go on a road trip. Mansfield is in a shopping center called Mansfield Crossing about 3-5 minutes off of 495, though if driving through the state, it would be an extra 10 minutes off of I-95 so most people would just continue to the Dedham, MA Tesla Store (though Mansfield is cheaper by $0.01/KW). Neither of which have anything near by, especially late at night, even in the way of restrooms. Though during the day they are both close to shopping plazas. Dedham being a couple blocks from Legacy Place, and Mansfield being technically in the shopping center but the farthest part of the parking lot from any of the stores (technically closer to cross the street for a different shopping center and restaurant). But I am getting off topic.
The point being Massachusetts does have a number of 50KW or higher stations from ChargePoint, EVGO, and Electrify America. Some as high as 350KW (a nearby Rhode Island station at a Walmart is $0.15/min at 350KW, which assuming you can sustain that speed would be cheaper and faster than the closest $0.25/KW Super Charger).
Now I like most people would love a CCS1 to Tesla adapter, but there seems to be some resistance there (though CCS seems to be more common for higher speed chargers currently). Though as there is aready a CHAdeMO adapter designed and working it doesn't seem like it would require much of a change to update that adapter for CHAdeMO 2.0 or the upcoming ChaoJi (CHAdeMO 3.0 900KW backwards compatible) connection. The other benefit to CHAdeMO is it is the only true international standard where the same exact connection is used globally (though also the bulkiest connection). So an adapter to the newer version of this standard would mean an US car that found itself anywhere in the world could still charge.
Now I don't know if any model Tesla could even handle charging at 350KW or the rated 400KW of the CHAdeMO 2.0 connector, but even if it was limited to the 250KW available at Super Chargers the option would be nice. And what would it take, maybe some thicker wires or an updated chip in the adapter? Likely far cheaper and easier to do than a CCS1 adapter from scratch, then again if Tesla wanted the adapter it probably wouldn't take that much engineering to make it happen.