I use a large 3 prong fanny pack, the sort that is favored by medical personnel without much issue.
I don’t ride RRR or Hulk. have been sent on a walk of shame back to lockers on MIB

. That time it was admittedly rather overstuffed with two water bottles.
Anyway, the following is courtesy of Orlando Informer but you might want to verify with Universal guest services department:
“For the safety of all guests, riders are not permitted to bring bags or loose articles on board certain attractions; in these instances, complimentary lockers are provided for the time it will take to queue and ride. At
Hollywood Rip Ride Rockit and
The Incredible Hulk Coaster, all items and bags must be stowed, and guests will pass through a metal detector before entering the queue. The only exception at these two rides is a lanyard holding your park ticket, which you may be asked to tuck under your shirt.
At other attractions where lockers are provided – including
Revenge of the Mummy,
Men in Black Alien Attack,
Harry Potter and the Escape from Gringotts,
Harry Potter and the Forbidden Journey, and
Hagrid’s Magical Creatures Motorbike Adventure – there is a little more leeway. At these rides, there are no metal detectors, but all loose items must still be secured in the available lockers.
If you are wearing a fanny pack (or “bum bag,” as it’s known to our friends across the pond), it will only be permitted if the bag does not interfere with the safety restraint of the ride vehicle, and this is at the sole discretion of the team members. If you have any questions, we recommend that you speak to an employee, who can advise you on whether you must avail yourself of the lockers – this is especially important if you have items that you need to bring into the line for medical purposes, and the employees can assist with this, too.”