Maxtra+ jug makes generic water filter cartridges incompatible - any alternative sources?

Been happily using Amazon Brita Maxtra compatible cartridges for several years. Now the jug has worn out so bought a new one. Everything looked identical, my Amazon cartridge fitted fine, but no water went through.

I now see that Brita has gone to some effort to make the old cartridges incompatible with a specially shaped matching valve, where the old design of jug just had a hole at the base of the top water container.The new design is called Maxtra+, the old design is called Maxtra.

Are there any alternative Maxrta+ cartridges around yet? Anyway, try not to get caught out buying the old design ones if you have the new design of jug.