One peer from Europe shared this adaptation for her year old son to ride with her on the back of her wheelchair. It uses commercially available baby carrier parts from BuggyPod (see link) on top of a Lascal BuggyBoard, a stroller board meant for a child to stand on behind a stroller. It requires no changes or only small adaptations (depending on your wheelchair) to clamp the BuggyPod Perle and BuggyBoard onto the back of your wheelchair’s frame tubing, but you must be able to get your baby in and out of the seat while seated in your wheelchair, which may take some practice.
