All I could find are invisible grilles on the net but not what I am looking for as in the pic.

I presume such design is approved by BCA.

Any good recommendation will be appreciated.

Horizontal grilles allow kids to step on as a ladder and climb over.

fall from height barriers require a “Barrier QP” to sign off as compliant to BCA regulations. I doubt any QP will sign off on this design these days. 

Building regulations these days are both “descriptive” and “prescriptive”. QP has to certify compliance. Some regulations are not clearly spelt out but covered under “descriptive” safe use.