Is the original download in you CP account history or do you have a copy of the receipt with the original download links to send to SMS?

If it shows up in your CP history, you should be able to buy the extended download service.  For a fee (last time I purchased EDS for software it was still under $15) you have unlimited downloads of the software for up to two years.

You may have to open a ticket as the EDS doesn't always show up in the catalog. 

If it isn't in your history and you have the receipt, contact sales at SMS and ask if they will sell you the EDS.