I need something with a crotch strap to keep his pelvis from sliding out and to keep the chest clip from creeping toward his throat.
E-Z also makes vests that might give him the support he needs.
If the seats mentioned by previous posters are not available or suitable, I would recommend the E-Z-On vest. We have been using one for a while and they are easy to use (contrary to the first impression of some people!) and very supportive.
We have the 102 model vest with the push button buckles at the front which makes buckling the vest very simple and quick. Here is the link to the page on the E-Z-On website:
E-Z-On 102 Model Vest
If you do choose to use a vest, I would recommend using the ‘
Floor Mount’. With a correctly fitted vest the attachment points at the hips will do an excellent job of holding the pelvis close to the seat bight and thus provide the support required. If the required size of vest does not come with crotch straps as standard, you can always have them fitted to the vest as option (either sewn or removable).
With the 102 model front-opening vest, we discovered it was possible to keep the vest secured to the seat, leaving the buckles open when it is not in use. This way when it is needed the person using it can sit down and simply put it on like a jacket. It also makes it easier to assist someone using the vest if they have trouble managing on their own.
Additionally, the vests have no chest clip, so there is no danger of anything coming too close to the throat.
The only factor to be aware of however is that you will need to install the heavy duty tether anchors to use the vest, if you choose the floor mount. If you opt to use the tether mount, then a heavy duty tether anchor will also be required above a certain weight (which is dependant on the factory installed vehicle tether anchors). The heavy duty tether anchors come with whichever type of vest mounting system you choose.
I hope that helps.