Tried designing myself but am still struggling with threads so I found this design and added the curved top plus holes. I printed in petg since butane is cold, I tested the one print without herb and it works well but the wall thickness at top needed to be thicker which I already fixed to 3mm. I only did 2 walls when printing but I will do 3 for next one. Also the first upload my printer did top hole too small so I drilled it out but second file I added 1mm to size of hole which printed out for the 2mm butane I had. The infill was good at 15% but I reduced to 5% with the 3 wall setting.

Still learning but this does work so if any issues let me know, I hope it prints well for you tho and enjoy.