Hello,
I am so sorry for your loss. I found this formula online:
"Chinchilla Milk Formula Feed
1 part evaporated milk
2 parts cooled boiled water
1 tiny pinch of probiotic such as Avipro Plus
1 tiny pinch of Critical Care powder
1 tiny pinch of Nutrobal (calcium and mineral supplement)
The above milk formula can be liquefied and presented via a syringe using the Hand-Feeding Method suggested. The formula must be at a temperature of 99°-100°F and only reheated once.
Very young chinchilla babies that are depending entirely upon hand feeding for their nourishment, must be fed every 2-3 hours, giving them one-half of a syringe of formula and upwards depending on their age. With older kits the feeding can be spaced several hours apart and 4 feedings daily.
When a chinchilla kit has had all of the food it wants it will appear to resist being offered any more by pushing the syringe away with the forepaw. Stop feeding at this stage as over-filling a kit's stomach can not only lead to digestive problems such as bloat but also cause juvenile mortality!
Formula can be made up and stored in a refrigerator for 24 hours before a fresh supply must be made. Take out the amount of formula you need and warm only once to room temperature." from
http://www.chinchillachronicles.com/weaning_a_chinchilla.html.
I'm not sure if that is accurate, but I believe it is a reputable site. Best wishes for you and the kit!