Duk Ling would have potential, though in her current state would be a disappointment to anyone with a bit of nautical knowledge, as she is now so under-canvassed. As she is at the moment, she is, also, almost iconic as a symbol of the Hong Kong tourist industry, therefore perhaps too well-known?

I have no idea what the cost would be to charter Duk Ling if she is currently still working in the tourist industry, or what it would cost to change her outward appearance a little to make her look a little more authentic, and I am not sure if the "Big Eye Chicken" type was ever used by pirates - but at least it would be starting with a genuine Chinese junk hull. If the film maker has a big enough budget to look at Hong Kong for a vessel and to be able to charter and dress up Duk Ling, then it is possible there may be other even more suitable prospects still available in Hong Kong. As far as getting assistance from JRA is concerned, I would suggest making direct contact with our member who lives there, who is very knowledgeable about Hong Kong junks and would almost certainly know what is likely to be available these days. (I am referring to John Kw).
Duk Ling is said to have been built in Macau and used as a motorised fishing boat. She was purchased in 1981 by Drs. Wayne and Teresa Moran who lived aboard until 1986 (see JRA Newsletters #17 and #21). The Morans then sold her in order to finance the commencement of a major new project: the building of a Foochow Pole Junk, and a plan to sail in the wake of Marco Polo in his voyage to deliver the Princess Cocachin to the King of Persia. That boat of Moran's, the Cocachin, would have been splendid and as authentic as could ever be found.

Unfortunately the Marco Polo voyage never took place, Cocachin was sold and last I heard was languishing opposite the White Heron Hotel on the Pearl River with a drastically cut down rig and some rather ugly additional superstructure.

With the right contacts in the appropriate Chinese Government department, Cocachin might still be a runner but once again, would need to be re-modified to look the part.
There are at least three other authentic junk replicas that have been built in recent years that would be perfect as they are - perhaps some contacts could be made from the UK through Chinese diplomatic channels.
In Mainland China there is an authentic "Green Eyebrow" type somewhere in Zhejiang Province (Zhoushan Islands) which would be the "real deal", not unlike Moran's original Cocachin. Would look the part superbly. Contact with the right people in Zhejiang Province may be possible through diplomatic channels.

Ditto Taiwan Cheng Kung which is an authentic replica in Tainan city (Taiwan) which was built to commemorate the famous merchant/pirate/naval commander who we refer to in the West as "Koxinga".

Taiwan Cheng Kung is a little less flamboyant but never-the-less a genuine sailing replica of an early type of merchant/fighting Chinese junk.
Precious Dragon was used in Hong Kong for filming work - rented out for making Kung Fu movies - later sailed to the UK and I believe she is now back in Hong Kong somewhere.

Her owner 20 years ago was Mark Cuthbert.
The perfect go-to person ought to be Dr. Wayne Moran (Cocachin). After Cocachin I believe Moran returned to his medical profession in Hong Kong, but continued an interest in building authentic junks and I believe was a consultant to the filming industry in this area. He used to be a member. Last I heard he was living on a boat in Hong Kong Harbour, but despite repeated attempts I have been unable to make contact.
As stated earlier, my suggestion would be, first, to start looking around in Hong Kong, starting perhaps with Duk Ling - and make direct contact with John Kw for his local knowledge and expertise. John probably doesn't follow the forum, but he is a member (and I think actually a committee member?) You need to be on the spot over there, or have good contacts.
(PS if filming also takes place in the US, then there are a number of replica junks over there which might be worth following up. US members?)