The cage on the elusive Suntour Superbe long cage FD-5800 and the cage on the Suntour XC are the same. The only difference is where the hole for the stop screw is drilled. So, you can buy a XC for cheap and make yourself a Surperbe long cage RD from a RD-5300. You'll need to drill/tap a new hole then move the stop screw.

VeloBase.com - Component: SunTour Superbe II (long-cage friction)

VeloBase.com - Component: SunTour XC