If you don’t mind drum brakes, find an HHR at a junkyard and take the hub assemblies, front and rear brakes. For the fronts you’ll need the calipers, brackets, dust shields, and rotors. For rear get the drums, all the springs and hardware, and backing plates. Not sure but I think the brake hoses on the Cobalt will work. If not they’re cheap to get. I would recommend getting new wheel cylinders and not try reusing old ones. I’d almost just recommend new calipers as well. But they may be expensive for anti corrosion coated ones. If you are to get everything new you’ll spend at least $600 using decent stuff. Maybe more. And ordering online, the shipping may get expensive unless you order from Amazon.
If rear disks are what you really want, you’ll need the rear beam axle from something like a Cobalt SS. I never find any with rear disks at the junkyards, so probably would have to source a new axle.
I’ve been thinking of doing the 5 lug swap since I got my Cobalt. If I decide to do it I’ll try and find as much as I can at the local Pull-A-Part, using the stuff from an HHR. By that point I’ll have to decide on aftermarket wheels or something 17” or 18” from a Cobalt or HHR. I don’t know and exact amount, but buying the parts together at the junkyard I like has the benefit of lowering the total price since they will group items together when checking out. So I’m probably looking at around $90-$120 for the swap, minus new pads and shoes which I’d rather get new. And depending on the condition of the front rotors, I can machine them and the drums. New ones aren’t too expensive.
Wheels and tires will probably be more than doing the swap itself. Be aware the drum brakes use a W shaped spring and can be a real pain to get it back into place. It’s the type GM uses a lot. But really if you’re used to doing this type of work, you can get it done all in one day. I still need to get a new abs motor for my car, so I’d probably do it at the same time.