Is it all right for a Christian to wear a slave bracelet?

Why wouldn't it be? Being a slave is not a requirement to wearing a slave bracelet. Additionally as slavery is outlawed most anywhere I don't think anyone would be tempted to think you are actually a slave to someone. If however you are wanting to wear it as a BDSM style, then my only recommendation to you as a christian wearing one, would be to follow the same procedures you would follow before having sexual activities with anyone. Be married to them first if you want to stay biblical, however you will find no where in The Bible where it condemns BDSM except in the practice of it not being contained within a relationship of two consenting married people.

Personally I say, if you want to wear one, find one you like and wear it, no different than wearing a bracelet of any other sort.