You can sell them anywhere (Namepros, Sedo, Dan ..etc) and push the domain to the buyer after sale is completed, so the buyer will have to create a Godaddy account if he does not have one.
It happened with me several times before (selling a domain during 60 days period), for example I had once a sale at Sedo where the domain was locked, I simply told them that the domain is locked and only push is available, and everything went smoothly.
But be aware to only do this with domains that are registered with a popular registrar like Godaddy, because everyone has a Godaddy account, if the domain is registered with an unpopular registrar then the buyer might not like that and may cancel or ask for refund.