Broncos memorobilia holders can add postal envelopes to their collection for Super Bowl 48.  Spokesman David Rupert says people can purchase the envelopes right now in Denver at the 20th street location or the Stapleton office on E 53rd.   They will soon be available in Fort Collins and Colorado Springs.  Order forms are available at all local post offices and the envelopes can be mailed directly to customers.  Rupert says many local post offices in Colorado are decked out in orange and blue for the Super Bowl.  He says the collectible envelopes should be a bit hit with collectors or anyone else who wants a Super Bowl keepsake. Cost is $10.00 per envelope.