Alternative to SD K/D

My mothers little Radar has been having issues, mostly stemming from the fact that he's 15 years old and his little body is just old and giving up.

His last bloodwork revealed high levels of createnine (I'm sure I butchered that) and I think elevated BUN, so the vet put him on SD K/D to try and level him out. The second round of bloodwork is due to be done this week, to see if his levels straightened out.

SD is gross. What good alternatives can I offer my mother, so Radar can enjoy the last year or two of his live?

He's very old and doesn't have much in the way of teeth, but I have access to just about every type of food under the sun.

Science Diet K/D has low protein levels, low phosphorous, and low sodium - so I would aim to find a WET (moisture is very important in maintaining kidney health) food that is low in phosphorous and sodium. The first one that comes to mind for me is Weruva - all their varieties are very low in both. The Lotus canned food would be another option.