Headlight burnt out rubber holder

Need help with 2011 Pruis issue:
The passenger side headlamp (low beam) bulb burnt out for whatever reason (could be that it was not seated properly when I last replaced it myself). It appears that the rubber or other material on the headlamp assembly around the bulb also burnt out as a result of the heat from the halogen bulb. The socket and wiring are good and I can put in a new bulb and wriggle it tightly into the hole where the bulb is supposed to go in...I completed a 1000 mile trip just now with the bulb held this way and it appears ok, only that the angle the bulb points in is not perfect creating some dark spots when driving.

The dealer says for $500 to replace the entire headlamp assembly. Is there some better way to replace only the rubber or the area that holds the bulb instead of having to replace the entire headlamp assemble? I could take out the headlamp assembly - I have seen the videos and it appears something I could do mysef...just wondering if I really need to replace the entire assembly which I see is being sold for around $100+ on ebay.....or is there a cheaper way to replace only the burnt out part?

Also if I were to get a replacement headlamp aftermarket assembly just for the passenger side, would that look like and match the original drivers side assembly or do both need to be replaced at the same time?