The top and bottom ones are both from Weather Underground. The US map is just: https://icons.wxug.com/data/weather-maps/radar/united-states/united-states-current-radar-animation.gif
For the top one, go to the radar site's page on Wunderground. Here's the page for ours: Fort Polk Radar | Weather Underground. Once you have the image setup the way you want it, scroll down to the bottom and click on Save Image. That'll open a new tab with your customized radar loop. You can use that URL for your image tile.
The one in the middle is from NOAA. I'm not sure if there's a more friendly way to find your radar, so you may have to go digging through here: Index of /ridge/lite/N0R. Mine is: https://radar.weather.gov/ridge/lite/N0R/POE_loop.gif. If you don't know the 3 letter code for your radar site, there's a list of them by state here: NWS JetStream - RIDGE Radar Downloads