What about one of those connector rings you use to attach toys to the stroller? My niece used to hold one to fall asleep.
ETA: Howell has this bunny ring. It's pretty small so I may feel safe to give it to him after six months. I give it to him for naps now and it, in fact, helped end our nursing strike. Sorry I can't make it clicky. It's called The bashful ring bunny by jellycats. My link is for the pink but we have the blue. He loves holding his ear. His name is Duncan since he is shaped like a doughnut. :]
https://jellycat.com/usa/sbb555pr/
Re: Soother?
ETA: Howell has this bunny ring. It's pretty small so I may feel safe to give it to him after six months. I give it to him for naps now and it, in fact, helped end our nursing strike. Sorry I can't make it clicky. It's called The bashful ring bunny by jellycats. My link is for the pink but we have the blue. He loves holding his ear. His name is Duncan since he is shaped like a doughnut. :]
https://jellycat.com/usa/sbb555pr/