There are bidet-like sprayers for spraying poop off of cloth nappies into the toilet[1]. There are also similar actual bidet attachments for toilets for adults[2]. I was thinking you could almost do the same thing as those and just make it smaller and low pressure.
[1] e.g. https://www.amazon.com/SmarterFresh-Diaper-Sprayer-Premium-S...
[2] e.g. https://www.amazon.com/RinseWorks-Certified-Warranty-Pressur...