This is the carry bar button for all Cameleon carry bars Gen 1 & 2 . The original Gen 1 button was squared off top and bottom but the better "self locking" design for the Gen 2 will fit the Gen 1 carry bar. Any hardware shop can get you a spring to fit if needed. I use 5/16 x 5/8 x .026 spring that comes in a handy pack of 3 for $5.00 made by the Century Spring Corp in Los Angeles USA Code on the handy pack is C-556. You may find the button is a bit stiff when first fitted but a bit of silicone spray and pressing in and out for a minute or so soon wears it in.
Another repairer in Norway has made a video on changing the buttons I've put the link below.