One of my favorite preps. If you're planning on having running water during SHTF, it cuts your "paper products" needs down to effectively nil.
At this price, even beforehand, it would probably pay for itself in a month or two in paper savings. It's also a quality of life improvement to me, but that's not really the prepper angle.
A little dinky "overstocks and closeouts" place up by my NEGA place has them for $8. I'll be back up on Friday, and I can't imagine there being a big run on bidets in rural GA over the next four days.
For reference, it's this one.
https://www.amazon.com/Luxe-Bidet-Neo-120-Non-Electric/dp/B00A0RHSJO/ref=asc_df_B00A0RHSJO/?tag=hyprod-20&linkCode=df0&hvadid=167148575413&hvpos=1o1&hvnetw=g&hvrand=4742016653723334058&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9010783&hvtargid=pla-274847307778&psc=1Pretty nice, actually. Comes with a self-cleaning knob, braided hose, and even the wrench to install it.
If you want me to grab you one, and you plan on seeing me between say now and say the Christmas party, let me know and I'll pick you one up.