I need some help with a battery powered light.

I used to go to RS regularly for test leads, sockets, bulbs, switches and other odds and ends I used in the electrical fault tracing classes I taught.
If I could find it myself on the shelf, great. If I had to ask I would get the same intelligent thoughtful look a cow has when chewing her cud.
Me: Do you have any of the 12V 3Amp power supplies?
RS dude: Duh, I don’t know, who is your cell phone carrier?
Here in So Cal if you aren’t buying a cell phone you are on your own in RS

They seemed to have good knowledge of phones. I hadn’t been in a RS for decades, when i went in one recently to get a free sprint cell phone upgrade. My sis went to the sprint store and had to pay some kind of refundable fee to get hers, while the shack waived that fee for me. I liked that.
Now, its my turn to be a befuddled novice because i’m shopping for a new cell phone service and dont understand all the lingo i should. So as not to look too dumb, i’ve spread out my questions to several sales points, including RS, so i can ask the same questions whos answers i didn’t understand - or looking for answers i want to hear. Gads, there are way too many variants to get my head around. I want the cheapest and dont want to pay for stuff i dont need, so i’m sure not to be a pleasurable experience for clerks wanting to make a hi dollar sale. So far, i’ve been a waste of their time. Google searches for the cheapest deals have steered me to sales bombs of the same useless data (looking for cows). Its amazing to me that prices are that high when there is so much competition out there.