How would you travel just about synthesizing amniotic fluid?

you know those fitness waters? that's probably pretty close. mostly water, beside some carbohydrates, electrolytes, vitamins..
you'll also find urea and amino acids, some fairly specific proteins, lipids, phospholipids, and some living cell. synthesizing these would require some very advanced life chemistry, probably beyond our current capabilities. it'd be at tiniest as easy to find those proteins and whatnot contained by other body tissues and isolate them, and WAY easier just to extract it from the amniotic sac (in small quantity, so the pregnancy can continue) as in amniocentesis. it does indeed replenish itself, as long as the mother keep herself well-hydrated.
amniotic fluid is a dynamic entity, though. it begins to hoard about fourteen days after conception (human gestation) and its composition change throughout pregnancy.
out of curiosity, why do you want to do it? if you just want to breathe underwater (can't remember the movie that proposed this possibility), not worth it. even if you collected ready-made amniotic fluid and tried to breathe it, it wouldn't work because you are not getting oxygenated blood from another source. if you enjoy some kind of medical application surrounded by mind. worthwhile cause but i can't conjure up it getting simpler than just extracting for a moment here and there from of a mind donors (some risk of miscarriage accompanies the procedure, but individuals get it done anyway for varied reasons so why not pick some of it?).