Maybe this is a bit of a stretch, but could it be worth reaching out to admin and seeing if you can ask about previous adverts on the site? Maybe there is a log they can check to help narrow down your search.
Another option that occurred to me, is to just embrace the brights and turn it into a colour palette for the whole image. Stylistically speaking, it's a fun challenge.
The art below isn't mine, but it shows the general idea!
With instances like these I will colour drop the palette from the character, then desaturate the entire work a little and put some coloured filter layers over the top of it. It takes a lot of the harshness out!
So long as you're not doing a flat-colour, there are subtle ways to tweak with your...