It maybe the photo, but it doesn’t look like you have enough counter overhang to accommodate bar stools.

The recommended counter overhang also varies with the counter height, with experts suggesting 15 to 18 inches for the lower counter and 12 inches for a raised counter. Whatever height counter you have and whichever kind of seating, allow at least 24 inches of space between each seat for your guests' comfort.

Clear acrylic.

What Sammy said.

Something backless, that can be "perched" on because the reality is that people will have to sit kind of sideways to eat at the counter. More likely people will lean next to the stools. (Which is fine.)

https://www.houzz.com/products/acrylic-ghost-stools-set-of-2-smoke-bar-height-prvw-vr~82593933

Stainless steal no back would also look nice.

I would break up the whites and gray with a natural wood backless stool.

Reagan Low Back Counter-stool by Kosas Home · More Info

Here, this is the exact stool I had in mind:

“One More” Bar Stool by Philippe Starck for Kartell at DWR

From the photos it looks like you have a monochromatic palette. Depending on what you mean by "cohesive", there's 2 ways to approach this.

One would be to keep within the monochrome palette. In this case go with something in the grey to black tones. The obvious choice might be to go with more white since you have a white dining table and kitchen, BUT adding more white furniture on the dining room side will create more vertical lines against the darker floor and be a visual distraction. You can consider a leather stool with a stainless steel frame but it depends on if there are other metals in the dining room already. The leather will add a bit of softness and provide added comfort.

The other option if you don't mind to have the stool stand out a little would be something in a natural wood / rattan finish as you already have that rattan basket on the bar. However I would go with something less "chunky" in shape as suggested by housegal200.

Some other things to consider when choosing the stool. Do you need a back or not? A back will give extra comfort but be more closed off to the dining table. Do you want something that swivels, allowing you to easily face the kitchen or dining room for socializing?

There’s also this if you’re not afraid to be bold:

It also comes in other (boring) colors, like dark grey, white or natural.

From the picture you do not have room for stools. Even if the table was gone there is no place for your knees.

I just saw that you want backless...sorry!

I agree with a couple of the other Houzzers comments...First, has to be backless and small. Secondly, I'd do something in a color other than grey, or white to break up the palette. These would look nice:

Elm and Iron Industiral Bar Stool, Set of 2 · More Info