Kit to close return line to increase pressure???

Okay I have a letro legend II I picked up really cheap for my pool, the problem is I have a 1Hp pump but I guess there are too many return lines as the pump moves slow or not at all. However if I cover one of the returns I am in business. So I was talking to someone and he said there may be a kit to block one of the return holes in the pool. Is this true does anyone know where to obtain this as i cannot find it. I anted to avoid buying a booster pump if possible.
Mike

If you have the adjustable eyeball type return, you can just turn it 90 degrees and it will pretty well shut-off that return.

Not sure we bought the house not to long ago and there is an old heater on it so I dont think it has an adjustable eyeball on the return. The pool was built in the late 60's