ᐅ Seal the gap between the shower base and the wall

Hello everyone,

I have a problem:

As you can see in the picture, one tile is too short, leaving a gap.
Now my plumber says that the too-short tile must be replaced with a longer one. The problem is, it’s already a full tile. This means all the floor tiles in the entire room would have to be removed and reinstalled to keep the grout lines consistent.

Long story short: Is there a way to create a gap between the wall and the shower tray to cover the gap shown in the picture? My plumber says he wouldn’t be able to seal it properly, or guarantee a waterproof finish.

It would be great if you have a reliable solution for this.

Thanks!