BOY! Am I with ya on the suction cup thing!
I just put together a little Riparium and the cups that came with the caddy were silghtly deformed and wouldn't work right out of the package.
I scrounged through my assortment of surplus parts and found some from an old powerhead that fit in the openings perfectly!
But they just..........sucked.
Yours is an easy and cheap DIY for sure. Another variant could be aluminum wire. It comes in a few different gauges. It's usually in the section where chain and coated wire cable are (I spend WAY too much time in the box stores, lol!)
When those suction cups failed, it got the wheels churning. When time permits, I'm gonna take a shot at bending a piece of scrap acrylic to form a hook and crazy gluing it to the back of a caddy. Moving the fish room to the opposite corner of the basement doesn't leave me with much free time right now though, so a couple of hooks just like this will do just fine for now.
"Why can't my wife see all of this stuff as an investment?"