[ccp4bb] What is the easiest/cheapest way to obtain a library of proline derivatives?

[Jan van Agthoven]

Sorry for being a bit off-topic, but I’m looking to transform the catalytic 
properties of a protein I’m working on by adding an aromatic moiety on one of 
its prolines. However none of the proline derivatives I find commercially are 
really interesting. Does anyone know what would be the cheapest way to obtain 
customized proline derivatives? Most companies ask for more then $3000 per 
compound (about half a mg).