I've just added a wiki page with the known-good portable chargers this sub is aware of:

https://www.reddit.com/r/evcharging/wiki/portable

Not a lot of 6-50s available, but in addition to the Tesla, there are two other really good ones with 6-50:

• The BMW does have a 6-50 option-FOR-FLEXIBLE-FAST-CHARGER) which is a little expensive, but it's similar to the cost of a Tesla-Tap so it's a viable option, and the chargers itself if pretty reasonable.

• The J+ Booster has a 6-50 option for a more reasonable price, although the unit itself is more expensive. Still Amazon has a coupon right now and the result is $605, only a little higher than the totals for other options and probably the nicest setup.