In a pinch, I've fed mine Chicken and rice (1:1), noodles, cottage cheese, green/string beans, Chicken baby food (not turkey, too high in purines). Best to add any of these to her low protein diet to try to entice to eat the right food too. Chicken is around 22% protein, but mixed with the other things, the Total protein for the whole meal will be less than 18% or so, so within most recommendations for LS.
There is a diet or two on the University of Tennessee LS website:
http://www.vet.utk.edu/clinical/sacs...rShuntDiet.pdf