What are the alternatives to SwissStop Blue v-brake pads We've got a tandem with Rigida Andara CSS tungsten carbide rims and Swisstop Blue v-brake pads. We're happy with the performance and life of both of these over the last 1000 miles.

The problem is that only Swisstop Blue blocks are recommended. I've been led to believe that other blocks will wear out too quickly on tungsten carbide rims, possibly leaving a rubbery deposit on the rims.

I'd like to know of more than one manufacturer or supplier (preferably in the UK) who can provide suitable replacement v-brake block cartridges, so that I have options if the Swisstop ones are unavailable or become expensive. I don't like being tied to a single brand for what should hopefully be quite long-lived rims.

Are there any reasonable alternatives?
Kool stop R9 Magura HS33 Pads are made to work with Rigida CSS rims.

Also  V-Brake inserts  by kool stop for Rigida CSS rims.