You know, I've never heard of someone molding new ones, but that'd be a great idea!
Does the hole have a bottom to it? Like, is it just kind of an indent the device slips into, or is it a true hole where you can peer in and see the inside of the pony? I was thinking you could stick some Model Magic in there and stick some wings into that. MM would be very easy to remove for if/when you find a better solution. (But would it stain the pony?) If it's a true hole, it'd be herder to get the stuff to stay, though.