Do a looksie on E-Pay, cheap old style X and K band units are available.
With a 12vDC power supply, you can have your very own source. Even if you
just buy the head without the counter, the 12vdc will supply the head and it
will put out.

Do NOT purchase the Ramsey "kit" for this applicaiton. While it may be fun
for a budding electronics wanna-be, it does not put out at a frequency that
will trigger radar detectors.

Jack