One of my tips would be the company ELFA -
www.elfa.com
They provide bars/grids and similar things in some bigger interior design stores. Just look up places that cater to shelves and racks for closets (garderobs inredningar)! "Svenska Hem" in Mölndal has a HUGE assortment and some COOP shoppingcenters carry them as well. Just look closely in MIO furniture or such. Be curious, ask around and see where they might sell them. They have them in whitecoated or plain metallic. I might attempt using their bars to build a larger cage for my boys. You can secure it with cable ties AKA Buntband well out of the possibly bored GP's teeth.... Otherwise email Elfa and aks them if they can provide you with a list of the ones closest to you.
As for Coroplastic/Kanalplast I havea lead on a company in Eskilstuna that MAKES it. Who knows, maybe we'd be able to cut a deal there.