Others have listed the UA routes if those don't work & assuming you want to keep it in Star Alliance...
-Lufthansa who operates both 747-400 & 747-8i (which will be around for a while)
-(via Facebook) it seems Air China is launching their 748 soon.
-Asiana has a few who have been getting subbed in on some US routes but no real frequency
-EVA seems to still have them from Seattle and maybe Vancouver or vv.

And remember on UA unless you are in BusinessFirst or GlobalFirst the Economy cabin falls short of what you have probably come to expect in 2014's air travel standards.