Hi Steve
I had a similar problem with a client some time ago; she couldn't get a replacement for her bath as the company had ceased trading.
I made a wood panel: If you chose to do this it's very easy.
First you need to make a template of the exact curve at the edge of the bath (assuming its not just a straight edge!).
From the template (if reqd.) make a couple of frames to match, one for top edge one bor basze and join these together at each end and in the centre somewhere.
Cut a number of vertical panels, the width will need to vary depending upon the radius of the curve.
if you look at my gallery (from hyperlink below) you will see a phot of the finished result.
Hope this is of some use
B Regards David