A few years back on an old car I had, rats ate through much of the wiring in the engine compartment. I fixed the wiring and then poured a big container of pepper and similar hot spices all over the engine area.
They never came back.
Yes, Steren repellers are available in the USA.
http://www.newteksupply.com/Steren-Ultrasonic-Insect-and-Rodent-Repeller_p_18950.html
There may be other Internet sources. I am lazy this morning so passed on the first one I encountered. Steren itself may have a page if you can find it.
Steren has a major catalog but no prices listed. http://sterenusa.com/wp-content/uploads/2016/05/2016-Steren-Store-Catalog.pdf the item is called Repeltronic. Around page 80, no details.
There may be other makers of similar devices. I report the only one I know about.
If you wish, you might do a forum search or Steren. I posted the Steren page a number of times, but it may have changed. Seems like under $30 at the time, prices tend to go up with time.
We’ve used an ultrasonic pest repellent against mice in the garage for years. Seems to work without disturbing the dog. Our version is pretty small and optionally battery powered, so it is possible to put it inside an engine compartment overnight.
Placement of the device is important because of how sound bounces around and how the sound needs to reach corners and nooks where rodents hide.
Another thing for mice in a car parked outdoors are cans of chewing tobacco. Don’t know if it will work for rats.
For mice, buy a few cans (like a package from Costco), use a screwdriver to punch a few holes in the top of each can, and mount them (I used looped duct tape) on stable places around the sides of the engine compartment. Mice leave and/or stay away. The tobacco will dry out, but you can drip in a little water into the holes to extend effectiveness. When mice are gone for a while, remove the cans and toss them.
Warfarin is the most common blood thinner for people with irregular heartbeats. I’m very glad I don’t need it anymore.
Went through this bigtime couple years back. Mice, rats, packrats, squirls whatever eating on my daughters cars outside. Found droppings everywhere. Tried everything to stop them. They were chewing wires - and they especially loved the hoses for the spray washers. Long story short believe it or not get some peppermint oil. Mix about 2 tablespoons with a couple cups of water, and spray it around anywhere you want. Smells good but all sorts of critters ( and bugs ) hate it and will stay away. Have not had a problem since.