3 year old outgrow harness!

[Luisa Primo]

Hello, I'm in Brazil and my 3 year old has reached 40lbs (he is a tall kid). He is calm and obedient, but he is still 3 and I wouldn't trust him in a booster seat without the harness.
However, there are no extended harness seats available in Brazil, every seat here (I looked at all the available seats manuals) have a 40lbs restriction for the harness use.
What do I do? Should I keep him in the harness over the weight limit? Or should I transition him to using the car's seat belt?

Additional info:
Child: 3 year old boy, 40lbs, 41 inches.
Car: 2014 Honda City with isofix
Current seat: Kiddo Adapt with isofix

 

[ketchupqueen]

My understanding is that you can use US or European seats there. It's not safe to use a seat over the harness limit, so I would import a US or European seat with a higher limit.