Missing subframe bolt (right rear)

Recently took my car to get control arms replaced and mechanic noticed that I am missing a subframe bolt near the right rear. Mechanic then mentioned how it may be difficult to find this type of bolt since it is very industrial and a very long bolt so places such as Autozone or Advanced Auto Parts likely do not have them.

I am new to this forum, but if anyone knows where I could possibly find this type of bolt or have had similar issues in the past, let me know. I am thinking about going to the dealership and seeing if they may have any spare bolts lying around, but this may likely be the most expensive option. Any advice is highly appreciative.

I've got a 2007 Chevy Malibu LS 2.2L FI DOHC 4Cyl vehicle.