Revival has a good selection, very reasonable prices, and options ranging from hand-knotted wool to washable. I've been happy with everything I've bought from them.
https://www.revivalrugs.com/collections/runner-rugs?refinementList%5Bmeta.custom_fields.shape%5D%5B0%5D=runner
I agree with the PP above that it makes sense to look for two 12' runners. A common size will be much more affordable, but beyond that, a 20-25' runner will be more prone to getting out of alignment and harder to adjust when it does, and more unwieldy to move if you want to take it up for cleaning. I also suspect if your hall is that long it doesn't need any more visual lengthening and two shorter runners, matching or coordinating, would balance the space nicely.