I've seen red/blue spoke lights and valve stem caps from foreign sellers on eBay; I don't remember seeing a red-blue blinkie, but there's likely a reason: if you're in the U.S., you are wise to always remember that law enforcement has the blue/red flashing light thing legally reserved: in other words, if you show blue and red flashing lights in many/most U.S. localities, you are legally considered to be identifying yourself as a police officer.
Assuming you are not actually a police officer, this means you can easily be picked up on suspicion of impersonating one. Likely? Not particularly, but if you're the one who gets nailed, it's worth one or more felonies that can and will follow you around all the rest of your life. That means writing that you were convicted of
impersonating a police officer every time you apply for a job, fill out a background check or get into other trouble. Explainable? Sure...but do you really want to have to? IMHO, if you're in the U.S., pick another color combo - pretty much ANY other color combo - but leave flashing red and blue to Law Enforcement. It's exclusively reserved for the police in just about all localities domestically. I'm guessing this is why you don't see such blinkies much, anymore. All that said, I'm not a lawyer or a cop - I just prefer to avoid coming to the notice of either party as much as possible