In the comments of https://www.thingiverse.com/thing:4747703, it was stated that a pure ammo holder would be nice too.

So I drew up a rail holder for 4 darts. Fusion 360 file is included. It has a nice friction fit on my blaster. I think you can fit two in he rail, giving a capacity of 8. Combined with the ammo holding sights (see link above) total extra ammo capacity will become 12, so two full reloads. Enjoy!
I think you could also place two of these on the top rail, but I don't have that many darts anyway.

I made a solid version, one with a hole in it to make it look less heavy (I think it actually adds material to the print) and a hollow version. In the fusion file you need to unsuppress only one of the two extrudes to get the variants.

Creality

Ender 5

No

No

200

10

Print the outside wall slow (20 mm/s) to get a good fit.