Hello. I have an autistic child aged 3 who has recently learned how to undo his highchair strap and try and rock it over while I make his meal. He is 15kg so on the upper end for most high chairs. As I am on my own with him at mealtimes I need a secure seat for him to stay in while I make his meal. He cannot just be left to play while I go and get food as he has no sense of danger and is very hyper. Equally he won't stay in the room with me while I make food . I'm looking for a stable chair with a harness that isn't going to bankrupt me. Anyone got any ideas?