I have a playlist on playpen ideas you might want to check out.
https://www.youtube.com/watch?v=w7hb...nMw9Ro6wJO-zmU
Like Ria says you might want to start off with a big cardboard box and see how it goes, this will most probably at some point get chewed but can be replaced for free.
The problem with the metal barred playpens is that a lot of hamsters can climb them and escape, some people turn them upside down so the material floor becomes the ceiling and they can;t escape, but you can't really interact with your hamster if you do that.
The best thing I have found is a big plastic storage box - the one I use is on wheels. Not ideal if you don't have the room for it.
You can always use a bath or just secure a safe area of your house. I block areas off with long pieces of cardboard that can then fold back down again and slide away.
Whatever you end up using/buying always make sure they are supervised as they can escape or hurt themselves.