Kidney Failure in cats - apart from prescribed food what else can I give her??

Hi, My cat Foxy, has been diagnosed with Kidney Failure. She had been drinking and weeing a lot lately, so mentioned this to the vet when she had to have her booster, he weighed her (she had lost a lot of weight) and he immediately took a blood sample, after a 10min wait in the waiting room (had convinced myself by this point that she was gonna have the worse thing ever!!), the vet advised that unfortunately Foxy has Kidney failure. After reading up about it on the internet, I am slightly more comforted that this is quite a common thing in cats, thats sounds awful that I feel comforted by this I know, but does also mean a lot of people have been through this and can give me some good advice! After leaving the vets with food specifically for cats with renal failure, and also a purse being about £80 lighter! I came home thinking that she wouldnt eat the food/our other cat will eat it whilst im out so wont know if Foxy has eaten it, and then there was the added headache of trying to stop Foxy eating our other cats food, which the vet said that she was not to eat. I asked the Vet what other food could I give Foxy, coz I know she will get bored of it, and he advised Coley (fish), and chicken. I was wondering if any of the vets on petstreet could advise of any other foods that I could give foxy, as we are sometimes away for a day or two, and need to leave some food with the cat sitter that she can put out and both cats can eat. I have to take foxy back to the vets in three weeks for ´the decision´ if she has not made any improvements. PLEASE CAN SOMEONE HELP!!!!! Many thanks in advance Cherry, Foxy and Loulou Xx