I would like to try my original pondmaster waterfall pump (that is supposed
to deliver more than 3000 gallons an hour) but can I get an adapter that
would allow my to connect it to the 2-inch pipe?

Yes. It's called a "reducer". Go to home depot plumbing section.

Is there an adapter that will go from 1-1/4 inch to 2"inch?

Yes:

Item# 26020 at http://www.usplastic.com

Click: Pipe & Fittings - PVC Pipe & Fittings - PVC Fittings -
PVC Reducing Fittings.

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