Sassy I started surfing as soon as I read this this is what I found so far.
Substitution for mother's milk
Sometimes this sad thing happens, that female dies after delivery and babies survive, but only for couple hours if you won't help them. Then it's very important, what you feed the babies in exchange for mother's milk, because mother's milk has many necessary components which babies need.
It's not usually good to put babies to another female who just have babies because it's not safe for the babies. So there is only one way - to feed babies by some milk formula.
There are more formulas for feeding babies, I have for you couple of successful from people who successfully fed babies and they grow to healthy degus:
Mixture for feeding babies can be made of evaporated milk mixed with camomile tea (1:2). Once a day add little honey (contains energy) and you can also add little oatmeal water. You can made more of this mixture and keep in in the fridge, before feeding just warm little of this to the body temperature. Use eyedropper for feeding (in syringe there is too big pressure and it's hard for such gentle use) or soak a piece of cotton wool in this milk and let babies suck it. Feed babies every 2-3 hours in the beginning (at night too) and lenghten the intervals slowly as babies start to eat solid food. After feeding, rub babies' belly gently with tissue (wetted by warm water) to help digestion and rub also rectum surroundings (they can't relieve themselves without this). And occasionally wash baby with warm water (by which you replace the tongue of the female).
Another possibility is to feed babies dog formula. It's alreay premade and relatively cheep so it may be easier. Feed it for about 3 weeks from birth, every 2-3 hours.
Except feeding it's very important to keep babies in warm, they could die of undercooling. It would be good idea for example to place cage (or bowl, you can keep babies also in soft nest from tissues just in bowl) with babies onto the heating (of course not too hot). If you have some more degus, lik father of babies, you can let babies with them except feeding, they'll take care of them and warm them, although not that good as mother would do.