EZJim

Pete D named my supplier I buy all my Seltzer water from Safeway - get the 12 fl oz cans though and NOT the one liter bottles. The best and most inexpensive (and how often do those two adjectives apply to the same item) is the Safeway in house store private brand which has Safeway on the lower right and SELTZER WATER in caps on the front of a blue colored part of the can for a label with a Lion rampant insignia. In my area, they have been running a six month sale of 4 six packs of the cans for $5 Don't get any of the flavored ones Safeway sells unless you crave sweet fruit flavors or lemon lime but I can't vouch for them.
Do NOT go to a liquor store nor buy any pre-packaged so called seltzer equivalents - as Patty warned, liquor store mixes are not really pure seltzer even if they are labeled as such or the salesman insists it is. Liquor stores only sell "soda selzter" or else "club soda" or "tonic water". They each have unnecessary added ingredients such as quinine, solidifiers, emusifiers, etc which will mess you up.