Yes, there's other ways to get it done.
Since you need a vise, or something similar to work with when using the tool, you can make your own from metal and measure and cut your own slot into it....or just use two pieces of straight metal (same thickness) across the opening of a vise or two boards of lumber. You can use a socket, that will clear the center button, to tap the cap down for removing it from the OE piston; once you've separated the OE piston from all else but the cap;