I would like to transition from a 1-1/2" diameter sch 40 PVC pipe to
just 3/4" diameter. Is there a reducer for this or do I have to go
from 1-1/2" to 1" and from 1" to 3/4"?

I'm pretty sure I've seen a reducing bushing at Lowes that reduced that far
down. The bushing fits in an elbow, coupling, or tee, and then you can
connect the smaller pipe to the bushing. I think I saw one for 1/2" too.

In any case, is there some reason you can't use two reducers in series to
step down to the size you need? It seems easier to me than special ordering
a fitting if you can't find it locally.

Anthony