Apparently there was a state rule for the NJ senator that he could not run for president while in senate. They changed it for Cory Booker. So apparently it is possible to add rules for senators and congressman.
On a federal level, There are safeguards we can add and perplexity to trading stock for congressmen. One such rule is the disclosure rule. This makes it a slight pain to invest. A second rule I propose is committee conflict rule, declare stocks that are in conflict with a committee hearing, and offer recusal to the chair each time on a hearing with a potential conflict. A third rule is prohibition on potential stock trades after a committee hearing for 90 days or until hearing is published. And do not disclose details of the hearing with anyone until it is published.
These rules add pains and discouragement to stock trades. But outright bans are not there.