How can I purchase replacement needle for Plato flux dispensing bottles?

Techspray does not offer replacement, only complete flux bottles. The needles are standard parts that are commonly used for automatic dispensing systems. You can find compatible needles with distributors like Grainger. They are 1" stainless steel needles, 21 guage for FD-2 and SF-2, and 26 guage for FD-21 and SF-1.