How can I authorizing a Sony PRS-300 Reader?

My ebook account (Sony) was recently transferred to Kobo Books.  Some of the books I've purchased are Adobe DRM protected.  This didn't used to be a problem before the transfer.  I don't seem to be able to authorize my Sony reader.  Is there any way this can be done?

The PRS-300 came with ADE.  Adobe discontinued supporting this model of reader which effectively made it useless for ebooks protected by Adobe DRM.  Other models of the Sony Reader continue to be supported.  I find it hard to believe that this particular model was axed when the same, or a similar, fix could have been provided.  Shame on Adobe!