Hi--as far as finding a close friend who is into it (or is interested to try), I have always found that this only happens naturally. No way to force it or push it. As far as more casual tie-up buddies... there are always forums like this, or personals (like bondage.com). Depending on what you are after, you may be able to find a "fantasy escort" to play with you... some escorts are quite familiar with tie-up fetishes! Over the years, I have tied up several lady friends and also several escorts. Different experiences, so all depends what you're after I guess.
Jeff