Here's a link to the sink I installed. It's a Blanco 441024. It measures 28x18x9. It easily fits into a standard 30" sink base.

Here is a link that might be useful: Blanco Sink

I just installed a 23" wide Kraus stainless steel undermount single bowl, rectangular with corners that are almost square but have a small radius for easy cleaning. The outside dimensions are 23x18. The inside dimensions are 19" wide by 16" front to back. It's deeper than average, too, at 10" to the underside of the counter. It arrived quickly in amazing packaging (including its own fabric drawstring bag!) so it was in perfect condition. It came with a rack to protect the bottom of the sink. I think it comes in other sizes and styles. I had never heard of the brand before, but it's very high quality and I'm thrilled with it.

Here is a link that might be useful: Kraus sink at Overstock

I just received this sink, which I believe meets your specs at 26"w x 20" front to back x 10" deep (with an interior width of 24"). It shipped quickly and reasonably priced and, although its not installed yet as I am still waiting for my cabinets, I am pleased with it.

Here is a link that might be useful: SS Sink

Thanks for the recommendations. I will check these out!