Fuzzbutts make good fleece hammocks and "snooze cubes" - well made so not so risky as some of the fabric ones (ie they don't have wadding inside and are stitched tightly without loose threads). He might like one of those - however you have to watch for chewing - if he chews it you'd have to remove it and then he'd be upset! I have a snooze cube for our hammy but I use it out of the cage - have to say it's a great way of getting him out of the cage - I just lower it in through the top door and he walks into it and I get him out that way. Or he walks into it if I open a side door when he wants to come out. My only concern is the rings for hanging it up, and the metal eyeholes in the corner - I snipped my hanging tabs/rings off. If they happen to climb on top they could get a leg caught if they jumped.
I did have a hammock and the snooze cube inside the cage for our last syrian, when he got very old and was beyond chewing things! For that I just pulled the eyelet rings through the bars and attached them to the bars on the outside with cable ties.
"Homer" mini cage furniture for your hamster,mouse,gerbil,glider
Those are the mini ones for hamsters - the other ones are enormous - although a large hammock might be ok. I'm sure he'd like a snooze cube! the double hammocks I have never quite managed to work out how/where to hang them suitably. The little corner hammock is quite small but it's what I had for our older syrian, low down in the corner of a cage.