I've finally done it – made my own lightbox – and it cost me practically nothing. I got the idea from this BeBetsey post so for more technical details you can go over there.
The pic above is the first one taken in the light box with no artificial light. The one below was taken in the same light without the light box. What do you think? Neither of the photos has been fixed (other than cropping).
Here are some pics of my lightbox. You can see I used a box (left over from a shift some years ago), some white card for the interior and 2 large sheets of white tissue paper to tape across the holes I made in the top and the sides of the box.
PS When I say I made the lightbox, it would be more technically correct to say that my better half did most of it – he is much more patient at getting the details right than I am!