Found this today at a "flea market" (actually a small shop): A toy metallophone with painted aluminum tubing from the 1950's in its original carton. There was a pair of mismatched mallets, so I bought a couple of new ones at the music store. It has a wooden frame with removable threaded and turned legs and leather strips under the pipes. It's diatonic (presumably in C) with a range of 2 octaves and a fourth!

I was at a DIY store yesterday and saw some similar tubing. It might be possible to calculate the lengths for the sharps and flats and make an "auxiliary" pipephone.

I bet my recorder students (3, nearly 6 and nearly 8 years old) will be thrilled with it (nearly as much as I am). I can't wait to get it home and give it a try. I've been wanting something like this for ages, but new metallophones are quite expensive (even the ones for children).