From what i've looked up, jello-shots are still ok.

http://house.mo.gov/content.as…..sHB62T.htm

(16)  Specifies that any person who possesses or uses a beer bong
or other drinking device used to consume similar amounts of
alcohol or any large volume alcohol container holding more than
four gallons of an alcoholic beverage on any river of this state
or who possesses an expanded polypropylene cooler on or within 50
feet of any river in this state except in specified areas will be
guilty of a class A misdemeanor.  This section does not apply to
the Mississippi, Missouri, or Osage rivers (Section 306.109);

That was the only section i saw that pertained to Missouri rivers.

Individual rental places could have their own rules as to what they allow in their equipment I would suspect.