i have found some external dvd burners that will do both the dvd +r dl and the -r dl. i was wondering if they made one yet that did both of these plus could use the lightscribe feature. where you flip the disc over then make a label on the dvd. has anyone found one yet? 
Just buy a lightscribe drive, and put it in an external enclosure!
If you don’t want to build it check with these guys, they might make you one.