I would think any officiant who does commitment ceremonies (if same-sex marriage isn't legal where you live) would probably be open to this. A lot of UU churches are poly-friendly so if there is a UU congregation near you, that may be an avenue to look into.
For our wedding we did a semi-traditional Christian ceremony, but also had a handfasting in the middle of it. The pastor wasn't familiar with that (shocking, right?) so we had the best man (his cousin) do the actual tying while the maid of honor (my sister) read the meaning of everything that was going on.
So, it depends on whether you want it to be someone ordained or not. Since it isn't going to be legally recognized that isn't really required and you can pick someone who knows you very well to personalize it. There is all kinds of info online about various ceremony styles so that you and/or the chosen officiant can choose aspects that fit you.