On Saturday, 11 June 2016 12:55:30 UTC+1, MM wrote:
Here is a picture of my holders, one in position on a pseudo
bookshelf.

They aren't transparent, and it will depend on the thickness of your shelves, but I've found a length of PVC mini-trunking clips nicely onto the edge of MFC kitchen units.

You could make something like this
http://www.gresswell.co.uk/plastic-m...l-holders.html
out of laminator pouches with one fold in, they wouldn't have to be springy to grip the shelves.

Owain