What I used for years and years (until I just got my official stethoscope) was just a "sounding stick". Basically any stick or rod will work. Often I would use whatever was lying around, a yard stick or any small stick about 3 feet long. I would hold it with my fingertips on the end and hold that in my ear. Works really well! Actually I find the stethoscope too loud usually. Main advantage of the stethoscope is you can pinpoint what you are listening to better.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra