2007 dodge magnum srt8 is missing all of the air sensors in the tires

I bought my Magnum SRT8 used and after a short while I realized that periodically all of the warning lights that are yellow come on in combination with a picture of the car and dashes (- -) next to each wheel where I presume the tire pressure would be displayed. I had it looked at, at the dealer. They charged my $150 to reset the computer, it didn't work, I gave up. Some years later I bought new tires and they told me that all of the sensors were missing. I have no idea why. They said that these are necessary to have the ABS and traction control to work right. They wanted $125 per wheel to get em and put em all in. Is this a fair price. I'd kinda like to buy the parts online myself and have them install them. Dose anyone know what parts these are? That's it thanks.