I would expect that the handle is more expensive than the charger and that you would not save much by buying separately.
Have you checked that it is not the current tooth brush that is damaged?
The Braun model4736 currently retails for £45 but if you only use one mode have you considered the Braun Oral-B Vitality Dual Clean Rechargeable Toothbrush for £17.50?
Neil S, February 2014