Iridium Sprinklers are the best type of sprinklers available in Stardew Valley, but you need a lot of crafting materials to craft them from scratch. However, it is also possible to buy them! You can actually purchase one each Friday for 10 000 gold. It's sold by Krobus, which is located in the sewers. You can only buy one at a time, and he only sells them on Fridays, so you can get one per week. This is really useful if you rater want to spend your Iridium Bars on other stuff.
In order to be able to buy the Iridium Sprinklers from him, you need access to the sewers. This place in unlocked once you have a total of 60 items delivered to the museum, so you better get donating if you want the sprinklers.