Here are some ideas with varying degrees of portability, not sure what size/shape you had in mind:
Here is an idea using hoop pvc pipe:
Hi! this may be helpful
Here's an idea for a mini greenhouse:
This is a cute one https://www.youtube.com/watch?v=Y35PVCHVQcM
Hi there, it depends on the size of your greenhouse and what you'll be planting but one of the easiest small potable greenhouses are made from plastic bottles in a wheel barrow. You can find a tutorial to make bottle greenhouses here - https://www.apieceofrainbow.com/21-amazing-diy-greenhouses/
Get a wire rack or low table and cover with plastic drop cloth clear tape the sides into a box to fit 3 sides then get another drop cloth to use in the front to roll up and use string to hold it
Whatever option you choose, be sure you can move it. In my area we need to worry about the wind moving things.
Here's an idea.
this link shows a lot of DIY portable greenhouses, just click on the one you want to try! https://www.google.com/search?q=diy+portable+greenhouse&tbm=isch&ved=2ahUKEwj-t-nJnqLoAhWLQDABHREzAHcQ2-cCegQIABAA&oq=diy+portable+greenhouse&gs_l=img.3..0j0i24.13683.15758..17024...0.0..0.127.462.0j4......0....1..gws-wiz-img.k8QnpKrdOcU&ei=XiRxXv6QPIuBwbkPkeaAuAc&bih=730&biw=1536&rlz=1C1RLNS_enUS874US874
Use Plastic Drain pipes and fittings to make your shape. Either use Polycarbonate or plastic roofing to make roof and sides or maybe even Polythene or Syrin Wrap/Cling film...................Best wishes.
You can make something like this, to go over boxes on wheels.https://images.app.goo.gl/6ZvWt2eT6hG99FvV7
Here's some great ideas for simple greenhouses that could be moved or stored