Yes there are reptile humidifiers . There called foggers or misters although alot of people do not recommend using them because they could "possibly" give your bp and ri. You can rig a fogger so it keeps misting the towels over the viv keeping get them wet and keeping your humidity up.
There are loads of different ways of keeping humidity up like covering the top, spraying regularly, some people use waterfeatures in there vivs to add to humidity
I've always used sphagnum Moss. IMO it's the best thing for humidity. I also have 2 water bowls one on hot side and one on cold side.