I tried finding study buddies on here last year, didn't fully end up working but it could be worth a try.
Otherwise, the best advice I got given around study buddies and study groups was that BoS is almost like one big study group in itself. And throughout my HSC journey I met fellow 2015ers and had discussions with them and really got a lot out of it. Also, if you do something like a HSC journal on here, you may find that's a big help