ST rear seat setup for ages 5+?

Hello! I know this has been asked before but wanted to ask it again in case anyone has new setups going on that they like and can recommend.

We just crossed 2000 miles on our LT and love it so much we added an ST to the family. I have a very wiggly 5-year-old that is going to be riding on the ST and I don’t fully trust him to be safe on the back with just the foot pegs and the bar to hang on to. I really love our LT set up with the cargo cage to hold him in (it’s also another layer of safety if I drop the bike or get into an accident)

What are our options for a rail bar or secure seat for older kids on the ST? We also have a Thule Yepp that we use for our 3 year old.