This is a great question and a really interesting direction to take your marketing... are you thinking of running a radio spot or just playing the jingle on your site?
I'm sorry I don't have a good answer for you but there may very well be a few VAs with the talent and skill who don't even realize this could be a potential side-service - maybe placing a little ad in our Classifieds
Services Required section would help track down one or two?
I do know there are a few VAs on the site who host podcasts and/or sing... it's worth a shot!