You wil not find the old "rock face" concrete block that were used for old basements at a reasonable price. One choice is find an old building in the area.
I assume you are adding on and trying to match the existing.
Those old block are only made in one or two areas and the price is high ($4.0 - $10.00) plus freight IF they match your pattern.
The new, colored architectural rock face block are much cheaper, but will not match.