I needed to raise the height of some office partitions beyond what leveling feet alone could accomplish. My solution was to create extenders from pieces of EMT conduit with a nut welded into each end. Rather than use the original levelers, which were dirty and bent, I made new ones out of a printed part and some bolts, nuts and washers.

For each leveler, you'll need:
(1) 3/8" x 2.5" bolt
(2) 3/8" washers
(2) 3/8" nuts

The legs are 1/2" EMT conduit with a 3/8" nut welded into each end. After my friend welded the nuts in, I cleaned them with acetone and painted them gray.