I have a couple of not-too-alternative questions that some one out 
there might be able to help me with.
I have just bought an elderly 5x4 enlarger for 30 pounds stlg (50ish 
US) from a junk shop. It is called a Prefect and was made by Rayham
Developments of London. It has a cold cathode head  but 
unfortunately the bulb has been broken.
I could either make myself a diffusion head for it or I could 
try and find a new bulb. (expensive I expect.)
I have never used cold cathodes before.
 Can anyone forsee  any  problem with using below-the-lens 
filtration for multigrade papers or for the production of separation 
negs for gums etc with a cold cathode light source?
Can anyone suggest where I might try and find a bulb or if indeed I 
stand any chance of finding one at all?
I'd be grateful for any comments.
Roger.