Thanks for the comments guys....appreciated !!

I found a fella on good old Ebay...specialises in bits for old British classic cars and bikes....and he had a set of clear lense's with amber bulbs up for a Buy It Now of £15'ish. Asked him to measure up and email me the dimensions and the only measurement that was a bit out was the fixing screw centres. Took a chance and ordered them... had to drill out the fixing holes in the lense by 1.5mm, but there is plenty of 'meat' to allow for this. Bought 4 of the 'chrome type' indicator bulbs from the local auto shop and the job's a good 'un !!!
Contact details for the supplier are... lotsofclassicbits..that's his ebay shop. I mailed him after I'd done the conversion to ask if he had any more in stock with a view to letting the forum know about him. He said he can get as many as is needed...just tell him Steve sent ya !!!
Link here...if it works !!!http://cgi.ebay.co.uk/Clear-Lens-Indicator-set-AJS-Triumph-BSA-Norton_W0QQitemZ190147878528QQihZ009QQcategoryZ25628QQssPageNameZWDVWQQrdZ1QQcmdZViewItem