CassyLouise,
A couple of options--we used small vials of sodium chloride from the pharmacy that had 20 ml in them. It was 14.6%, 50 mEq. The endo told us how many ml to give total daily and then we divided it up into the bottles. This stuff did not have to be refrigerated and keeps until the expiration date on the bottle--like 2 years!!
Another option that we changed to at about 6 months--plain old table salt. Your endo should be able to tell you how much per day--ours was 1/5 tsp. We just kept that in a small container and sprinkled it in the bottles (and later the food) throughout the day. I’ve also heard people dissolve the salt first, but if you are adding it to liquid--it shouldn’t matter--just mix it up well.
Hope this helps--email if you have more questions.
Cassy