I think you'll be pleased to know that you can probably still get them today. If you can't find them in the states, I might be able to source one locally for you here in Taiwan. I've seen them before.

As for subsitutes. As fastsky said, WM Supersports 40 is an excellent plane. Kyosho has the Calmato low-wing trainer, which I think is about the most beautiful low wing trainer today. My friends fly two, one with a YS53 and the other with a deisel engine. Both have raving review for the kits. The person with the YS53 on his is very experienced with pattern ships and twins in his hanger often comes with only this plane to the field. He says that it is the easiest building ARF he's ever put together and everything was spot on accurate (he measured all critical areas) and it flies just as well.

I love WM models but this Kyosho's got this class of plane sewn up!