Because version 3.5.3 is quite old (dating back roughly a decade or more), it is considered "legacy" software. However, many enterprise systems running on Java 6, 7, or 8 still rely on this exact version to maintain stability.
JasperReports versions prior to 6.0 are hosted on SourceForge. jasperreports-extensions-3.5.3.jar download
On Windows (PowerShell):