Would help if you defined what YOU mean by "Radar". Measure distance to a single object? Detect presence of a object within the sensing range? Movable target? Fixed target? Full 360-degree "picture" of surroundings? Narrow beam or hemispheric?
For object detector (intrusion detector) check with local alarm equipment supply house ... they have a bunch of indoor and exterior rated units. Depending on nature of target, IR detector and Ultrasonic are also alternatives.
If you're referring to distance measuring, as in tank fill (vertical application), there are lots of those also.
