I'm a firm believer in using that which is durable and roadworthy- especially for a doubler.
Try Yamaha YSS-475. Easy to play and durable, while not too harsh on the wallet. If you can afford it, step up to a YSS-675.
Whatever you get, invest in a good mouthpiece! I've always found the Dukoff D6 a very nice, easy one to play. Or, if you like hard rubber better, try a Selmer Super Session "F" or "H".
Good luck!