40mm shotcup for airsoft

Put one 40mm OD 35m ID 5mm thickness O-ring on each groove, and technically it should work. Since most launcher tubes are 39mm thick, silicone up the O-ring before inserting it to the barrel.
For the top I'd suggest a cutout carboard paper, it should do the job.
Be respectable to nature, use PLA for printing this.
The length is 90mm for this model, outer diameter is 37,5mm



Source for O-rings: https://tinyurl.com/y9mkajtz