What could i use as a retainer for my piercings?

I am getting an mri tomorow. i have 17 piercings and i would like it to stay that way. i dont want to take them out during the mri because i dont know how long it will be and i dont want any risk of them closing. i bought two lipring retainers for my indurstrial. i was only able to get one in, but thats not the point. i wanted to know what other things you could use as a retainer. i over heard the person at the place i bought the retainer say that he used a fishing line (obviously a new clean one). i was wondering if thats actually workable. please let me know any ideas you might have. thanks! :D