I don’t know if the 32-bit freetype2 develop headers are all you need, they’re in your OSS repo so all you need to do to install is the following
zypper in freetype2-devel-32bit
If that isn’t sufficient, then you can install any of the 32-bit freetype2 rpms from Factory (TW).
I don’t think that installing just these rpms should damage your system, you won’t be installing anything that will alter or should affect your LEAP. Links to the freetype2 i586 rpms can be found on the following page