Hi again Allmodeller, ok i went to Dohome (do nothing home) and they have whole units but no replacement tubes. They had one model there which had a screw in tube of ABOUT the same dimensions as you stated and the model number of the TUBE was D-3-G or D-G-3 (piece of paper blew out of pocket on the way back

, the THREE assistants (make that no assistance) would not allow me to remove the tube to check the actual dimensions so i could let you know exactly . (they were truly as helpful as a lead lifejacket

and yes i do speak reasonably good Thai). The only other place i can think of is diagonally opposite Mak In Haeng Market on the southside near Siam Pharmacy is a large electrical supplier/wholesaler who seem to have a huge range..the younger daughter speaks some English so maybe if they dont have it they could order it for you. Im sorry i cant be of more use to you mate but at least it saves you a trip to dont DO anything to help HOME.....sheeeeeeesh
cheers mate
dozer