I have a set of brand new front brake pads for my 99 celica they are the CarQuest brand, Ceramic Pads GNAD476. I am curious if anyone knows what other vehicles these pads might fit on, I no longer have my Celica.

Take any other compatible pad, such as Wagner QC476, and check that.
LEXUS ES300 1992-1996
LEXUS LS400 1990-1992
LEXUS SC300 1992-1998
TOYOTA AVALON 1995-1997
TOYOTA CAMRY 1992-2001 (V6 only)
TOYOTA CELICA 1994-1999
TOYOTA SIENNA 1998-2003

eBay is pretty good about listing compatibility.
https://www.ebay.com/itm/Disc-Brake-Pad-Set...6-/191616760315

I like to use Rockauto to interchange.