Storage Areas Free-Standing Hay Holder?

I apologize if this is in the wrong place, I couldn't think of anywhere else to place it.

I do not have a barred cage, I have a DIY cage made of wood and plexiglass. It basically looks like a table stacked on another, with a 4in tall plexiglass wall going around the entire structure. Because of this, I have no wood backing or bars to attach a hay bag or rack to. I used to use hay bags in my past cages, but I obviously cannot do so now. So instead, I am looking for a hay rack/holder that can either stand on its own or can lean on something in the cage. If it's going to be free-standing it has to be heavy, as you know, guinea pigs like to knock things over. I'd prefer it to be DIY, but it not it's fine

Thanks in advance!