Raised wall-hung planters

This year we planted our strawberries in two 36" hay troughs. Great, but they're not in the best situation. I'd like to get them into a hung trough on our south-facing boundary.

That boundary has standard fencing along it's length (concrete posts with six foot wooden panels). So ideally I'd have something with brackets that could affix into the concrete posts for a stronger hold. I saw this: Elevated Raised Bed Growing Platform. It looks like what we're after but the sizing doesn't quite work.

What I'm after feels like it could be standard or at least that there could be a modular system for this. Does anyone know of anything please?

 

Could you attach a length of timber to the concrete posts, then put the hayracks on that?

The hayracks I have just have holes at the back [they're plastic rather than metal] and you just put screws onto the wall/fence to hang them on, so it also depends on what design your racks are. Even if they have large hooks, those would fit over the timber.