You will need an intermediate Mac capable of running a Classic Self-Extracting Archive from Apple's download site, and then you'll need a USB floppy drive for your Macbook to write it out:
If you don't want to go through this yourself, system disks are offered for sale here (not my site):
The article below contains information about how to create 1.44 MB Mac boot floppies under Mac OS X. Without having tested this procedure at all, I cannot say whether recent system versions would work or not.
Otherwise, the easiest way would probably be to locate another older (pre-1998) Mac with a built-in floppy drive for 1.44 MB (and possibly with a direct Internet connection). JustSomeGuy provided you with links to two 6.0.8 (1.44 MB) downloads. A utility called StuffIt Expander can be used to decode downloaded MacBinary (.bin) files on the Mac in question. After decoding and decompression, one can create sector-copied floppies from the resulting disk images via (the Make A Copy button in) Disk Copy 4.2.
If it is absolutely impossible to locate another older Mac, one could even use a Windows PC with a floppy drive (an appropriate version of Aladdin/StuffIt Expander for Windows, and a disk-image utility like WinImage, would be needed in order to make sector-copied 1.44 MB floppies).