Hi Nid,
In India the best thing to buy for the squirrels as food would be Choostix Petasure Lactocer for Puppy and Kitten Milk. You can get it from Amazon India. For milk Royal Canin seems fine.
For the 1CC syringe/or any other syringe you can get it at any local pharmacy shop which are plenty in your area.
For rehydration you can use simple WHO ORS widely available at any pharmacy or given free at govt dispensaries. Same dilution as for human adults is fine. It is the osmoles that matter brand is irrelevant. Do not use D5W. Normal Saline or Ringer Lactate would be better options. Pedialyte name is a misnomer as it can be used in any age group regardless of what is written on the label.
As the temperature there is quite warm already do not put them in too many towels as the babies will overheat. Ventilation is very important.
If you can afford you can order fortidiet 5 lbs pack(approx 2.2 kg) = 8 USD
https://www.amazon.com/Kaytee-Forti-...ortidiet+mouse from Amazon USA as some sellers ship it to India (Rs 550 plus shipping compared to Rs 8000 if you buy it from someone in India). It will be way cheaper than anything you can find in India. I would visit the local vet clinic and check with them what they use for rodents. You can also buy EBSILAC from Amazon USA or some other websites as I checked some sellers ship to India. Note however to expect a 4-6 week period for delivery no matter what shipping you choose unless you use FEDEX or UPS which will be not worth it. I send many packets to India and I know the costs very well. Good option in-case you may need these in the future just find the cheapest and get them shipped via normal mail.
USPS is the cheapest option and basically the shipping is more expensive than the products in most cases. I would send you 10 pounds of fortidiet rodent blocks if you would be willing to pay for the shipping. I will also add in a box of EBSILAC. That is the best I can do. I am expecting a shipping cost of 60-70 USD for these based on my experience but due to the weight it could be more. I can check with my local USPS if you get interested in my offer. Shipping is a killer to India sadly.
Do you have any contact in Himachal Pradesh or Chandigarh area?
Best.