So my cat likes flowing water, I hear many of them do. We got sick of him screaming at us until we followed him into the bathroom to turn on the water...only for us to forget about it until three hours later, the middle of the night etc.
My goal was to make a watering system for under $10 and I think I just about nailed it.

My BOM as follows:
Plastic Bucket $1
Plastic plate $1
Set of funnels $1
Submersible water pump $7
https://www.ebay.com/itm/Mini-Submersible-Water-Pu...

Shoehorn (optional) $Free
16" rubber tube $Free
5V power adapter from old Roku

Step 1: Cut a Section of the Bucket Away

Your cat needs a place to insert his big stupid head

Also cut a V-section away for the power cord and water tube (and whatever you use to support the tube)
Re-attach the cut-away section 180 degrees away from the cut.

Step 2: Resevoir Cover

To be perfectly honest, I didn't use a plastic plate, it was a bowl. Since I didn't get a picture of it before I cut it...you get a plate. Cut that bowl/plate to a diameter that will wedge down 3-4 inches from the bottom of the bucket.
Cut your center hole the size of the funnel spout you like the best, then more holes radiating out from the center for splash drainage.
Fasten your cover with a small screw to keep it level

Step 3: Assemble!

So you don't have a shoehorn, third world problems... find any flexible semi-rigid (coat hanger?) part and rig it up to point the hose into the funnel, it makes the most noise pointing dead center so it's ok to be off.