You would not believe it but I would try Target. They are made for the kitchen, so they are back to prevent sliding and have some designs that might go well with your cabinets

Ballard Design has some unique rugs. Often times a wool rug will be wonderful in a kitchen as it resists staining due to the wool having an oil coating on it from the sheep. Try Tuesday Morning possibly or Home Goods. A remnanat outlet can cut and bind an exact length for you in your choice of their remnanats. There are also I think they are called GelMats.com for comfort on the floor. I have indoor outdoor runners I bought at Home Depot, very utilitarian in navy blue. I scrub them outside twice a year with soap scrubber brush and the hose.

I tried Target but will look again.

6ft runners are very hard to find - in my search, I found that 8ft is the most common length offered. I eventually found a 2ft by 6ft runner at Home Decorators Collection online. You can also try Overstock and Wayfair - both have large selections.