70 x 23 is hardly a "scrap size"...you may need to look into a slab purchase.
Your best bet is to go to a company that does counter tops. There are tons of them all over the place. They may have what your looking for, But like KMS said, the larger size may end up coming out of a larger slab and you will pay a lot for it. But many companies have tops that were ordered in which they goofed and may rework the top at a reduced price to remove it from their inventory.