I've just come across this firm in Scotland... I've sent an email enquiring about their Aluminium tubes.  I'll let you know the response

Peter S

Roger Taylor is using a municipal street lamp for MingMing 2.  I seem to recall from his video he got hold of the manufacturer by contacting the highways department of his local council. 

Might be worth a try.

Peter

hello    any idea where to buy  2x 50ft steel masts and 1x 40ft    street lights,  flood lights,  lamp posts , new or used   I am in Scotland but uk would be ok .....  also any used big sails for sale .......... trying to convert 45ft steel bruce Roberts offshore... thanks  andy