I was in the process of doing the very same thing. Originally, the tandem had steel raked forks, but I wanted to upgrade to discs all round so got a set of Fatty tandem forks, these had no eyelets for a front low rider carrier so i got some clamps from Tubus that fitted on the fork legs.
These were ok, but not very aesthetically pleasing and despite protecting the fork legs with pieces of inner tube and tape, the bolts marked the paint work which caused water to penetrate and blister.
I got some solid aluminium bar and made a couple of brackets which I JB welded on, drilled and tapped the centre for the fixing bolt.
Just need to prep for paint and the jobs done.