Seems there are no 32-bit download packages on Oracle's available download list.
UPDATE
Can download here:
wget --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/9+181/jdk-9_windows-x86_bin.exe
Answer
Although the 32-bit binaries for JDK9 seem to be missing from Oracle's lousy, unencrypted download page, if (after clicking "Accept License Agreement") you copy the URL of the 64-bit binaries and change x64 to x86, it will give you the 32-bit binaries.
Update: And now it's gone. Bizarre! What is Oracle playing at? They went to the effort to fix x86-specific bugs for Java 9, they explicitly said 32-bit Windows and Linux were supported, they list installation instructions for 32-bit systems, they made 32-bit builds fully available throughout the pre-release period for testing purposes, and nothing in their JDK 9 migration guide indicates that 32-bit platforms have been dropped (quite the opposite in fact: it says the -client VM command line option has been dropped so the faster -server VM is now the default for 32-bit).
So why are they suddenly hiding the release binaries?
I happened to have downloaded the Windows JDK (including JRE) and the Linux JRE for x86. I don't have the Linux JDK. There's an Oracle digital signature in the properties of the Windows exe so you can see that it's genuine. I do hope Oracle get their act together.
- jdk-9_windows-x86_bin.exe: https://drive.google.com/uc?id=0B4RBD9LUbdlvUHpESXdEMmdudkE&export=download
(SHA256: 62b9bc12ea64e9edb9950b0c784a1561b8503f7384270659ad93d66f1b3b456a) - jre-9_linux-x86_bin.tar.gz: https://drive.google.com/uc?id=0B4RBD9LUbdlvb0dtOHR0eDVoQWc&export=download
(SHA256: 372fbd6d8dc70c8087c0d3547f58d593266cf26cc4f6c6698b808930b3a4018a) - jre-9_windows-x86_bin.exe
(SHA256: bbd0e75dc6360e903dd905f080e1a1d76c9c78a27d9f7dd153c6e3adc6ebc78e)
Update 2: Apparently Oracle has decided to eliminate support for x86 Java forever. They somehow finished, compiled, digitally signed, and published the Java 9 binaries by accident. The binaries still work, but presumably will not receive updates.
Update 3: Apparently Oracle has become so hateful and hostile towards Java developers that they have compelled Google to block the above downloads with a DMCA request. Nothing I can do. Sorry. If you have Java 9, you have it, and it will still work. If you don't have Java 9, well, you'll have to get creative.