The cheapest I found one was from mothersdirect. If you are an ABA member you will get a discount from them too

You don't "need" a nappy sprayer. I lived without one for a long time and made do with scraping off with an old spoon and rinsing in the laundry. Most of the time I forget I have one and am scraping it off in the laundry still. I think I'm a bit immune to poo after 4 kids though rofl.