I use concrete reinforcing wire panels found at building supply stores. They're rusty and blend in. Cut to size.

I use extra tall tomato cages for my peony I found them at Lowe's

The largest grids I have been able to find are 24 inches diameter. For my larger peonies I use metal rims from rotted old wooden barrels. I buy a metal electric conduit which is 10 feet long and cut it in half making a stake for each side. Al

Nothing I've found is large enough for my largest, so I'm trying an idea I found here on gardenweb...Thank you woodyoak!
I have a ring made for my largest peony--if it works well, I'll watch craigslist for copper tubing and make them for my others. Unfortunately, copper is at an all time high right now--hopefully no copper thieves will find my rings! DH commented on how that is quite an expensive garden accessory...but nothing is too good for my peonies!

Here is a link that might be useful: copper peony rings

Tell your DH that welding equipment and classes on how to properly use it cost more than the rings. You are saving money by not visiting the emergency room for burns.

I use cages that I make myself from the garden wire I use for my dog runs. It is fairly heavy, 4 ft high, 2 x 3 inch mesh and I buy it in 100 ft rolls at the farm supply company here. A roll makes about 20 large cages. Can use it for tomatoes, cucumbers and squash too. :)It can be cut to any height and joined with regular garden wire or twist ties. I leave it on all winter and fill it with leaves to protect tender perennials.

Hi fellow Ottawan. I use the peony rings found at the Dollar Store, but instead of the spindly little stakes they provide, I pound a sturdy wooden stake into the ground behind the plant, and tie the ring onto the wooden stake with strong garden twine or wire. I put them on early in spring (in fact I left them in the ground this winter) and raise the rings as the plants grow to keep them under control. For smaller plants I simply enclose the shoots and the stake in the ring, and keep them altogether. This works for me.