I think Dikki has probably the easiest solution, using a set of bass peds since he is using triggering with one finger already, just would have to get used to using one and sometimes both feet.

I've seen a stick on midi pickup (not sure who sells them) that could go right behind the bridge on the 12 string, but I also don't think it would be a easy chore to get it to recognise because of the acoustic resonance of all those strings......pose