Save for a junior cassette- which I think is like 13-25, your options are making your own, or emailing Harris about their "century" cassettes.

Bicycle Cassette Gear Clusters from Harris Cyclery

Edit:WHOA, just clicked the pricing on those, not for the faint of heart, though two 6500 cassettes to kate your own should be around there too.

E2: you could buy the 14-25 and the 11-30 from this link and DIY: https://www.universalcycles.com/shop...06&category=41