Rockauto.com has the coolant recovery tank for 23.79 and it is an ACDelco.

 

There are several glue/patch products available.
One I've used is JB Weld.

Drill a small hole at the ends of the crack,
rough the surface (sandpaper) up,
apply a generous (mix) of the two chemicals after a good stir,
let cure completely and see if it holds under the heat.

This is a very simple cheep way to fix this, IF it will hold to the type plastic the tank is made of, but you do have to R/R the Tank yourself.

You might do a search of other products that are specific for plastic repair.

 

*UPDATE* -After the coolant reservoir was replaced the car was running cold, still no heat. Until yesterday it red lined hot and back down to cold repeatedly. Drove the 1 mile or so back to the dealership. When coming out to look at it, noticed a coolant puddle on the ground. The rep shook his head and said "this is why I wanted to replace the reservoir" hope you didn't fry the engine trying to have someone else replace the reservoir". Hopefully they call today and tell me it's something on the drive train that's covered on the warranty! It appears to be leaking from the left of the engine.

 

Hi there,

Very sorry for this! Any updates from the dealership? We would be happy to assist you further if necessary. Looking forward to hearing from you soon.

Patsy G
Chevrolet Customer Care

 

Did you do it yourself or have someone else do it? It's a pretty simple process and that seems like an awful lot of problems for that little fix

 

Hello, I figured out give General Motors another try and bought a 2013 Chevy Malibu with only 17,000 miles on it in December 2016. The car has been running decent but now I’m starting to see puddles under my car. I took it in to the dealer and they told me my hose is leaking going into the heater core. They quoted me $511 plus tax to repair. They charge me $70 to put another clamp on it and said that may work. Well it is leaking worse and worse now and I’ve looked at it and it looks like it’s dripping out of the bottom of the reservoir. It looks like there’s also stress cracks on the reservoir like I got Crushed before it was installed in the vehicle. Of course it’s not covered under the drivetrain warranty that is still on the vehicle. I will talk to a few mechanic friends and see if we could do this A little less expensive. I have no idea why the dealer would’ve told me it was a hose leaking that is very hard to get to and will take three and half hours to repair. Makes me lose my faith in Chevy because I would actually install a crushed plastic reservoir into a new car. Also the dealer doing a bad diagnostic.

Are use my phone in a selfie stick to take a video. I wish I could post a picture on here to show the cracks.

 

Over The Years, Vibrations And Pressure Changes Will Form Micro Cracks...Letting Air Into The System....REPLACE TANK CAP AND HOSE Underneath it...JUNK yard $10...DO NOT PATCH WITH SILICONE OR JB Products...BEEN THERE DONE THAT...Lasts About A Week...