Look at the Nissin MG80 Pro Canon. It uses a quartz tube to handle heat better than your old gear. You can find full performance benchmarks on the Nissin Digital support site.

You might want to consider the Godox V860III-C TTL Li-ion Flash for Canon since it's cheap, but be careful with the hot shoe pins tho, they can sometimes lose connection mid-shoot.

Honestly, Ive been in your shoes where gear dies right before a big gig and it is pure stress. Since youre on a deadline, the Canon Speedlite EL-1 Lithium-ion Flash is technically the top choice, but that price tag is basically a down payment on a car. Over the years, Ive moved away from the expensive Canon-only gear because the value just isnt there anymore. I have been using the Godox V1-C Round Head Speedlite for a long time on my 5D IV and the TTL is surprisingly reliable. The recycle time is insane because of the lithium battery pack... way faster than the old AA days. If youre worried about sync issues, just make sure the firmware is updated and youll be fine. You could buy three of these for the price of one EL-1 and still have money left for a backup. Good luck in Seattle, you got this!