I think I found what I needed. I will know when I've tested it.
From BOL on Integration Services job steps:
Use 32 bit runtime
Indicate whether to run the package using the 32-bit version of the dtexec utility on a 64-bit computer that has the 64-bit version of SQL Server and SQL Server Agent installed.
You may need to run the package using the 32-bit version of dtexec if for example your package uses a native OLE DB provider that is not available in a 64-bit version. For more information, see 64 bit Considerations for Integration Services.
By default, when you select the SQL Server Integration Services Package job step type, SQL Server Agent runs the package using the version of the dtexec utility that is automatically invoked by the system. The system invokes either the 32-bit or 64-bit version of the utility depending on the computer processor, and the version of SQL Server and SQL Server Agent that is running on the computer.
So apparently I don't need to install anything extra (if I'm reading this correctly). I can just tell SQL that this needs 32-bit runtime instead of 64-bit.