So I made a trial zipper pouch (but I can't stand unlined things so I put a cloth lining inside which wasn't in the original pattern).
If you want to make your own here is the pattern that I used. Sadly it is in French but the pattern is simple enough that you can figure it out from the numbers and the pictures.
If you aren't up for the brain damage of figuring out the pattern basically it is an upside down hat with a zipper in the opening so I am pretty sure any newborn hat pattern would work.
Or here is my best attempt to explain the pattern in English.
R1 - R15 (use bottom color)
R1 - ch2, 6sc in 2nd chain from the hook, place marker
R2 - 2sc in each sc around (12sc), place marker
R3 - *2sc in 1st sc, 1sc in next sc repeat from * (18sc), place marker
R4 - *2sc in 1st sc, 1sc in next 2 sc repeat from * (24sc), place marker
R5 - *2sc in 1st sc, 1sc in next 3 sc repeat from * (30sc), place marker
R6 - *2sc in 1st sc, 1sc in next 4 sc repeat from * (36sc), place marker
R7 - *2sc in 1st sc, 1sc in next 5 sc repeat from * (42sc), place marker
R8 - *2sc in 1st sc, 1sc in next 6 sc repeat from * (48sc), place marker
R9 - *2sc in 1st sc, 1sc in next 7 sc repeat from * (54sc), place marker
R10 - R15 - 1sc in every sc (54sc), place marker
R16 & R17 (use stripe color) - 1sc in every sc (54sc), place marker
R18 - R28 (use top color) - 1sc in every sc (54sc), place marker
Sew in zipper by hand (and lining if you want - I covered the ends of the zipper with fabric too for a nicer look).
Things I would do differently next time:
- Make my zipper a little smaller so the mouth of the pouch isn't as stretched
- Make my lining slightly shorter so that there isn't so much fabric inside
Here is another one that I crocheted - it still needs a zipper and lining - in the first one I made a mistake in the pattern and the bottom wasn't as flat as I would have liked but I did this one correctly (as typed above) and it looks great.