Peter, How about this cheap heating element. Fits inside a 1/4" copper tube perfectly.
http://www.ebay.com/itm/350505999493?ru=http%3A%2F%2Fwww.ebay.com%3A80%2Fsch%2Fi.html%3F_from%3DR40%26_trksid%3Dm570.l1313%26_nkw%3D350505999493%26_sacat%3DSee-All-Categories%26_fvi%3D1&_rdc=1 Jojo
