I think you could find several hardy or semi hardy fuchsias that could be trained up a trellis - they are not naturally climbers. But whether they would grow to the 12 feet you want is uncertain. It's possible but I wouldn't bet on it. The tallest mine ever got in a shrub form was about 10 feet after many years. And some will never get close to that height They can also die back some in a cold snap.

I'd consider Fuchsia regia, magellanica Molinae or Mrs. Boothby as good contenders.

Cistus Nursery carries regia but you'll just have to hunt for the others. Most of mine over the years have come from plant sales or my local Hardy Fuchsia Society.