If I can only get 500 ml per N2 cannister, I dont think this is as affordable option as I thought. I did find a set of nozzles where the smallest was 3 mm.
then I found the NitroBrew system that comes with its own air compressor but costs $350 which is cool but way out of my price range.
https://nitrobrew.com/product/16oz-nitrobrew-home-kit/
The only way this can be affordable to me is using a N2O cartridge. I can get a 50 pack for $25