I have an orphan

Four or five days ago, my feral cat had kittens in my old, non-running Rover. I thought it was a good, safe place, but for whatever reason, Mama did not, and moved the kittens. All but one. When it had been alone for six hours, with no sign of mama, I rescued it. Mocha is living in a box with me, being bottle-fed. The one and only time I tried this before, I wasn’t successful, but I did not have the special milk nor bottles then. I do now. Maybe I will succeed this time. Maybe not. maintaining the 90 degree temperature required is impossible. All I can do is keep her covered up, and hope.