If you are looking for a cover lifter that does not attach to you spa you should look at a basket style lifter.
These lifters have a foot that slides under the spa. The foot takes the weight of the cover instead of the cabinet. These can also be a good option in a situation where there is limited access to the other sides of the pool (where the pool is up against a fence or wall for example).
A basket cover lifter requires around 66cm clearance, more if possible, on the side that the lifter sits on.