I would say that ALL vets have red rubber caths. I am a LVMT (licensed veterinary medical technician). If you want to send me your address, I can get one for you. I also keep a handy supply of syringes here. Let me know and I can mail the stuff to you tomorrow.
I agree that she doesn't look so bad yet. Try putting some liquid vitamins or pedialyte in her water. That may help her also (if she is drinking). I have gone so far as to soak a weak baby in pedialyte in order to hydrate it.
One more thing, I personally do not like cutting the red rubber catheter shorter. The smooth round end is MUCH easier on the snake's esophagus than the cut end. With a long tube, you do have to prime it first. Before feeding the baby, be sure that the tube is full of food, then feed 1/2 to 1 ml. You should moisten the tip of the tube before gently sliding it into the throat of the snake. Also, you will want to gently advance the tube a couple of inches or so into the esophagus. If you don't then a lot of the food may come back up and that can make it easier for her to aspirate the food into her lungs.
By the way, If you can get a weight on her, I can probably get you some meds to add to the food to try to help with the RI, as well.