Sensor Engineer

I am in need of a non-contact liquid level sensor for small drums. I found that Madison Co. has created a ultrasonic sensor with a range of 4” to 70”, it be used on 30 and 55 gallon drums and requires no software installation or programming. I was wondering if anyone knows of any other companies that make such a sensor so I could compare them and see if they are worth buying or if I should make my own?