Taking you at face value, I checked out this site. They don't have ventriloquist, but maybe "throw voice" works. I asked a friend (on FB) who knows ASL, but she's probably sleeping.

My son's girlfriend and I both are rusty, and yes, we are interested.

What's the difference between a ventriloquist and someone with laryngitis? One throws his voice and the other threw his voice OUT...

Mrs. Doohickie used to be an ASL interpreter. She didn't know if there was a sign for it and said you'd probably have to finger spell it. She's going to check her ASL dictionary (computer CD).

Confirmed: Not in the dictionary, therefore, finger spelled. Someone current in the field might know a sign if it's kind of new sign.

The person I know also said it would have to be finger spelled.

The person I know isn't deaf, but has learned/used ASL since she was in middle school. ASL is somehow involved in her degree (Master's). She uses it while she teaches and is going for her Doctorate and it's involved with that as well. She's told me but my memory is for shit. In any case, she is current with ASL - uses it every day.

I also have an aunt who taught at the Oregon School for the Deaf, but she's been retired a while.