Yes it looks like it would be quicker to modify a Pope catcher than try to locate a Ogden catcher, it shouldn't be too much trouble to shorten the catcher to fit ,a few images from online to see the shape of the brackets.
Another thing I didn't mention before was the Pope has a deflector plate when the grass catcher is used to make collecting grass more efficient ,you could make a deflector plate if need be ,I've used push mowers without the deflector plate and the catcher still got filled with grass, the Ogden looks to have a deflector plate too when using a catcher.