Satellite 5 API - getting 'source' packages

Hi,

Using packages.findByNvrea I can find the specific installable packages I need then use packages.getPackageUrl to get a download link, but whilst there is a .src.rpm associated with the package visible by the web interface (at the same id), I can't find out how to get the filename/url/anything via the API.

Is there a call I'm just missing or is it not possible?

Stuart