Mine were non working when I first purchased the vehicle, so I cleaned out the bores with a needle.
Since then, I've only used rain-water in the water bottle, and the original nozzles are still working perfectly.
In my case, the problem was 'lime-scale' that had been deposited by hard water.
Sorry, I can't help re replacement parts.
2014 PHEV Aspire, Arctic Silver;
Hayman Reese removable tow bar;
1.5kW Solar, grid connected.