So Koko appears to be a Naka SIM (bottom of their website lists NAKA AG). There's a whole section on them at the
prepaid data wiki, though it's not listed there. The most interesting within that family though is
DrimSim, which has €0.01/MB data rates for Europe, the US, Australia and NZ, and lower rates than Koko for other countries I looked at. It's €10 for the SIM card delivered (no credit) vs. 20 Swiss Francs (€17.34 today) for the Koko SIM (no credit). Some of the screenshots of the DrimSim app show a top-up option of €10 which is nice.
One thing that's not clear is the phone numbers included with each. I think it's a UK Isle of Mann # for the DrimSim. GadgetKen, maybe you can answer what number came with your Koko SIM?