It is common for gamblers to bet a possession rather than money though.
This is why players should be able to set the bet amount. If they want to bet items they should decide beforehand, and maybe place the items on the table, then set the amount to 0 tria. Winner takes the items. If the loser doesn't pay up or tries running off with the item, it should be considered stealing and punished accordingly.
If you don't trust the other player, you could always have a trustworthy third party hold on to the items for you.