Prohibit any Congressperson or anyone in their family 2 generations past or future from making any transactions on any stock for an entity or any of its subsidiaries that has any current awards or pending bids/awards with any federal, state or related governmental entities for a period of 24 months (735 days) before and after the purchase date of the stock. Should any company that the congressperson has purchased stock in enter into the bidding process or be awarded any contract/agreement with any federal, state or related entity within up to 24 months (735 days) after purchase by the congressperson, that purchase is null and void and the stock shall be surrendered to the company or sold at the price originally paid by the congressperson (i.e. there shall be no profit or loss on the sale of said stock).
Further, no congressperson may invest in any company or any of a company's entities that is in any way or manner regulated by any federal or state regulatory body (governmental or private). Should any congressperson own any stock in a company that is regulated by any public or private federal or state entity (including existing stocks owned by the congressperson prior to their election), such stock shall be liquidated at the price of the stock on the day prior to their official announcement of their candidacy for congressional office.
This includes any blind trust or similar arrangement that may be in place to manage the congressperson's investments.
Or you could simply mandate that upon election to the House, Senate or presidency that individual must move all of their investments out of stock of any individual company and into mutual funds indexed to a domestic stock exchange and managed by a nameless, faceless bureaucrat.
Any violation of the foregoing shall be punishable by mandatory impeachment. Upon a finding of guilty, the individual is stripped of their office, ineligible for federal office at any level for the remainder of their life (this would admittedly probably require a constitutional amendment), and the case subject to being forwarded to the Department of Justice for criminal investigation. A conviction in federal court carries with it a mandatory sentence of 10 years in a federal supermax facility.
“Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy. It's inherent virtue is the equal sharing of miseries." - Winston Churchill