Get one from behind the toilet tank or vanity if possible.

We have thought to get a tile from somewhere else in the bathroom, but were told due to the size of the tile it would likely break.

Can you find larger tile in a similar color and cut it down? You'd lose the rounded edge on two sides, but that beats anything else I can think of.

Maybe buy the white and paint it biscuit.

I had a similar situation years ago and that's why now I always save back tiles in case they are needed.

What I ended up doing is to break apart the tile and made a mosaic. If I remember right it was centered with the spigot though. So in your case I would consider removing and breaking apart the ones on either side too. It looks like the one on the right is already broken too.

Do you have any extras of the top trim tile? You could use those tiles or similar trim tiles to replace the missing plain 12" tile. Or try a 12" stainless steel "tile" cut to fit. Talk to the professional tiler about how to waterproof the repaired area.

By the way, It looks like there may be a missing toilet paper holder. There are self-adhesive toilet paper holders that don't require drilling into your tile. Like this: https://www.amazon.com/DGWHYC-Drilling-Bathroom-Washroom-Stainless/dp/B08F9KV87V/

You could knock out the tile all the way to the top trim piece and pick something complimentary to make a waterfall effect. But I would worry about how well it could be waterproofed.

If it were me I would put a Flexstone (do it yourself or handyman) or Sentrel (professional network of installers) kit over the top of it and get panels to cover the other tile in the bathroom also.

https://flexstoneproducts.com/tub-shower-surrounds-2/

https://sentrelproducts.com/

The kits have lots of positive reviews on Home Depot and Lowes.

But we wanted a custom fit so we called Flexstone ourselves and bought direct. My husband installed it himself as it really is cut and paste. You can tell them your measurements and buy panels to cover all the tile in the bathroom. They even have a remodeling trim piece with extra depth to cover the panel and tile.

You can install on top of tile as described in the FAQ. https://flexstoneproducts.com/wp-content/uploads/FlexStone-FAQs.pdf

We love ours. No grout to clean. No possibility of leaks because we know exactly how it was put in. We got a corner seat (which I am so in love with), a corner shelf and a niche with a built in extra shelf.

I would be concerned about the waterproofing behind the tiles...not sure how you will make the shower surround structure waterproof by just replacing the tiles...

Remove the adjacent left and right tile as the right is apparently cracked anyway and replace all three with a piece of solid color solid surface. Forget color match please; not happening.

IMO you have already damaoger the waterproofing it there ever was any so why not bring the space a really nice update and replace the tiles and it will also give you some good new waterproofing and the accent tiles along the top of the wall are not ideal either . I honestly see not waterproofing where the tile was removed so a big red flag for me.