i have bought an old kiwi explorer with to see if it will fit peters VAd in the toddler seat (before anyone jumps on me i have sold loads of stuff to pay for this, and it wasnt that pricey, cheaper than buying a new standard tandem). comparing it to my old e3 which i sold, i have to say i prefer the kiwi explorer. the back seat is slightly higher off the ground, the frame is more robust and it steers better, the seats are wider, and the foot rest if better. the newer e3 folds up slightly smaller, and i think is lighter. it may also be easier to set up for baby and toddler, but i havent tried with this one as no need.
and there is one on ebay now. just the single, but the doubles kits are still available. go on, someone save themselves a bundle and buy the one on there.