Don't know what your budget is but did you look at the DaVinci cranks?
http://www.davincitandems.com/comp.html#cranks
With rings they are $550. For about $100 more they will black anodize them.
Another option is to get single bike cranks and have a helicoil installed so you can put them on the other side for the sync chain. This may be the less expensive option. Installing a helicoil is about $35.