Passenger headlight boot for halogen lamp

I've just replaced the halogen headlamps on my base 2008 Prius and discovered the passenger rubber boot that is supposed to cover the lamp is missing. I had purchased the car used 18 months ago and have had no problems.

I'm concerned because even out here in LA, we do expect rain late next week and I would hate to have water find its way to that headlamp and short something out.

Can someone provide the part number or a place where I might get a new or used boot?

Thanks.