Friction fit inline clip for the X-Shot Flux that uses 2 12x8x2mm o-rings, or electrical tape to create a seal. It holds 4 darts, and reliably fires one at a time. It should fit without removing the dart post, but that may restrict airflow too much so I recommend removing the air-restrictor and dart post entirely.
It also fits up to one o-ring into the barrel of the older X-Shot Recoil/Kickback/Pulse/Adventure Force Hypershot/Recoil (these are all the same blaster under different names), but the air volume pushed by that blaster is just slightly higher and fires the first two darts at the same time.
UPDATE: I updated the insertion peg to be slightly thinner, because I ran into an issues where one of the o-rings came out of alignment during insertion and stretched out causing it to to become stuck between the barrel and the thicker portion of the peg, making removal of the inline impossible. It probably could have been avoided by using a bit of lube, but I updated the design anyway.
The author marked this model as their own original creation.