Where should i sell marriott vouchers for 2 free stays anywhere in the world?

I tried listing them on ebay and apparently it is a listing violation to sell vouchers for something that doesn’t have a set location. I would rather list them in a auction since it would be hard to set a fixed price since marriott’s can range anywhere from 89 to multiple hundred per night. Any ideas on where I can put these up for auction online?

craigslist

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