A 1/35 AH-6 was issued by Dragon and has been rereleased, discontinued, and rereleased again. Latest is it has been discontinued, but you may find one through the various online hobby shops or eBay. There was supposed to be a multi-media MH-53 PaveLow (I know you said CH-53) but it seems that it will not happen.
The 1/35 Chinook from Trumpeter is a go and should be out sometime this late summer/early fall.
HTH,