I'm not Jewish and have no idea of the customs or acceptable.... well, anythings... of the Chuppah, but I have an idea for recreating this one (in a freestanding format):
You'll need four poles (see note below), a length of clear tubing equal to your desired circumference and smaller in diameter than the poles, 2 pieces of PVC that's thin enough to bend easily, one male/male connector for the tubing, 8 "T" connectors that fit snugly over your poles and allow the clear tubing to move freely, heavy-duty zip ties, and whatever fabric you want--organza, maybe, or some sort of netting?
*NOTE: Make the four poles from PVC, in whatever thickness you think best. (Alternatively, if you're nervous about or don't like the look of PVC, galvanized pipe can be found in the plumbing section and is pretty inexpensive too.)
What to do:
1. Cut your poles to the height you want the ring at the base of the top to be, allowing a bit extra to splay the legs for balance upon setup; set aside.
2. Cut tubing to your desired ring circumference, if it's not already.
3. Slip all 8 "T" connectors over the tubing. (You want the tubing to go through the cross-part of the T, if that makes sense.)
4. Connect the two ends of the tubing with the male/male connector.
6. Insert one end of one remaining PVC piece into on of the Ts on the circle. Have someone hold that end so it doesn't get away from you if possible and lay it across the center of the circle, then push on the other end to create an arch. when you like the height of the arch, mark the end you pushed on. (I don't know how to make this make sense; you want it to hook into one T, go across the circle in an arch, and hook into a T directly opposite.) Take the piece out of the T and cut it, then mark your second piece and cut it a little longer (to allow room for one piece to arch over the other in the center)--remember, it's better to cut it too long and then cut it down than to cut too short and not be able to undo it.
7. Insert the pieces you just cut into alternating T's on the circle, leaving the remaining T's free for your corner poles.
8. Use two zip ties to hold the two arch pieces together at the top of the arch, if necessary.
9. With the help of that handy-dandy stuff-holding friend, insert your corner poles into the remaining T's and stand the whole thing up, splaying the bases of the poles out a bit for balance.
10. Cover the whole thing with your chosen fabric, and tie the fabric about halfway down the poles (like you would tie curtains).
Now, I have no idea how much of this makes sense to you, but it's very clear in my head!
If you do have any questions, just let me know. Good luck!