Strider Balance bike brake

[designndrive62]

Might be a shot in the dark and apologies if it's against the rules but I am looking for the rear brake kit for 12" strider bike st-2 / st-3.

My two and a bit year old is now at the point where he is really confident and any slight incline is an opportunity for warp speed, but as a consequence dragging his feet on the ground is no longer enough to stop him!

I know there was a kit made, but I cannot find it anywhere that isn't sold out and it looks to be discontinued. I've tried FB, eBay, gumtree etc. Has anyone on here got one they may be able to part with or know where I might get one? He's not quite tall enough to transition to a 14" pedal bike yet so we just need a brake to get him through a few months.

Thanks in advance