There is one mobile vet in Cheras. You could call SPCA. Last time they suggested him to me.
If you can't find a vet: maybe you could learn how to test the glucose level on your own?
I found this online: "Home testing of glucose levels can be done with a similar type of blood glucose monitor used by humans. This method requires a small sample of blood that is taken from the cat for testing and generally provides an immediate reading of your cat's blood glucose level."
"Most diabetic cats require insulin injections under the skin once or twice a day, depending on the diabetic severity, type of insulin used, dose, diet and other factors. Because each cat reacts differently to insulin, your veterinarian will most likely perform a blood glucose profile at various time points during the day to determine the proper insulin dosage and treatment program. Insulin dosage may change over time as the cat ages, and you may need to adjust the dosage based on new blood glucose profiles, test results and how the cat responds to therapy. It is very important to consult with a veterinarian before making any changes to your cat's insulin dose."
I think you could learn that on your own. It's nearly the same with humans.
here the link to read more. You can also find additional links on this website
http://www.mycathasdiabetes.com/treatment.html
regards, Blueblue