You need to source a local offset printing company, or digital printing company.
Offset often has a higher minimum as they use printing plates that need to be set up, but much greater quality. It also depends on the design. You can get away with a lot using digital printing and is much cheaper.
With personal experience, I'd suggest getting samples of each type of printing first!
If your city?town? doesn't have a printer(s) then check online for printers. Such as Vistaprint (I have not used them personally) but just an example for cheaper online services. Or cafepress or zazzle etc. where there might not be minimums. Anything with a dye cut needed offset printing services. Any standard cuts A4 A5 etc. can be a digital service.
It depends on design of sachet envelope, colours, is it a photo? or a tricky design, will it be in the rain or not, etc. can all affect choices of printing.
(personal experience here about printing for example things that needed to go to some major presentation that would be kept by the person reading it, this type thing were offset printed, but their copies were done digitally for bigger production that would be looked at very quickly and not kept by that person, if that makes sense).
