What would you do in this case?

So, yesterday was unexpected, we rescued a beautiful kitten from the streets! She’s about 46 days old now. My heart broke when we saw her sitting in quite an unusual way with her hind legs behind her and her head down. It’s hard to describe the position she took.
She was just sitting helplessly, and the conditions of her surroundings were dire. She probably hadn’t had food or water for quite a long while. If ever.

We asked a random security guy what’s up with her, he told us she was standing outside the door of a supermarket, when a random man (dickhead, I might add) slammed the door on her, he said it broke her legs and her waist so she’s been in that position for a day or so. The reason I say ‘dickhead’, is because he saw that, heard her cries of pain and did nothing about it. He just left. I understand that most people can’t really afford to provide care for a cat, but you never walk away when you hurt an animal.

Naturally, we took her, gave her water, and took a dr’s appointment. When I arrived home I fed her, bathed her, then took her to a Pet hospital. They carried out some X-rays and the bones weren’t broken, dr said she’s paralyzed from the waist down. And that if we care for her she might regain sensory feeling. She got her vaccinations etc.

So now I have 3 beautiful kittens, 2 of which are Siamese.
What I’m concerned about, though, is how to deal with where she excretes. Obviously after we found out she was partially paralyzed, we knew expecting her to go to the sand tray is no good because she can’t control when she does it.

How would we deal with it, should we carry her there ourselves at regular intervals? How would you deal with it? Are there any special beds/pads etc.?