Cylindrical bass traps are fun to look at, but they are not as effective as a corner trap if you plan to place them in a corner anyway.
But, if a corner trap isn't an option, then a cylinder can be made fairly easily if you have some tools and basic building skills. The best I've experiences were made by making a thick piece of wood, like a few 2x4 pieces glued together to make a 12 x 12 block, then cutting it into a 12" diameter circle. With two of those, you can take chicken wire, or some similar open metal material, and cut use the wood circles as guides to roll a tube of the metal, stapling one wood piece to one end. Then stuff the tube with fiberglass batting and then staple the other piece of wood to the opposite end. After that, wrapping it with a open weave natural fiber fabric of your favorite color, stapling at the top and bottom, and if you want it to look nice use painted MDF as a cap for each end. With one of these at 4 to 7 feet tall placed in each corner of the room, the bass will be damped a bit and clean up the low end a bit.
But, you could also just take 4" thick traditional compressed fiberglass or mineral wool panels and mount them across the corners of the room and absorb more bass.