The M7 (Size 1156) is correct for the 2000-UP Toyota Celica turn signal... I know this sounds crazy, but all 1156 bulbs, wherever you buy them from, are the same shape - they need to be modified for installation into the 2000-up celica.
Here are a few links to different discussions concerning the 1156 Turn Signal bulbs.https://www.celicahobby.com/ubbthreads/showflat.php?Board=UBB4&Number=41054&Forum=UBB4
Install is simple, just choose what connector on the bulb that you do not want, and using a cement wall or curb to rub it off also works well (or use a nail clipper to clip that "nub" off) Your bulbs will then fit perfectly.
If you take out your factory bulbs and inspect them - you will see that they came with a "nub" on either side at one time or another. Then that extra nub was removed so that it would fit into the socket correctly... Go look at your stock light bulb and see for yourself
This is the same technique that everyone uses to install aftermarket 1156/M7 bulbs.