I have not found a reason why Mac\'s find does not have the option -printf. Apple normally decides to take options out which are not orthogonal to the other commands?
Alternatively, you could just
find . -type f -exec stat -f "%z %N" {} \;
Granted, this isn't how you would do the same thing on linux, but works for MacOS
find . -type f -exec stat -c "%s %N" {} \;
produces similar (not same, but close) output on linux.