Yes, it is possible - I did that once to a 1334 Junior. It made bag changes much easier and cleaner. I was always a bit surprised that Hoover took so long to realise the benefits of top fill.
I used the bag fill/support tubes and cloth outer bag from a U1104 Junior.
The 1334 bag suspension spring was too long for the set-up. I used a loop of string or twine, an inch or two long. I suppose a Turbopower Softbag bag suspension spring might do.