Tips for baby chairs??

Our little guy is getting diagnosed with CP this week, but it’s something we’ve known is coming from the start, since he had a stroke at birth and was in the children’s hospital for a few weeks following. It only impacts half his body, but he is 8 months and currently does not roll too much, and cannot sit independently. When I’m solo and going to have a quick shower, I normally set him in a momcozy chair with an arch of hanging toys. However, I find he’s now too big for it and has passed the weight limit. We have a fairly small bathroom so I can’t just set him on the floor on a mat, plus he also gets super frustrated on the floor solo. Any tips on a chair that can be used for kids over 20pounds and can securely strap them in?