I used VRBO.com, FlipKey.com, AirBnB, and a couple of others to find a place. There probably won't be much left, and certainly very little at any kind of a budget price, but it may be worth a look in case there have been cancellations.
Some options I considered were:
VRBO:
#348472 Mark, minutes away from Pechanga 4 bedroom/3 bath (1King,3Queen,3 full baths) 8 max capacity (I asked him, and absolutely no more) 5 nights (12-17) = $1545 Deposit: $500
#480724 "Panoramic Views/3 Acres/Walk to Wineries! Ave. $240 Nightly, Weekly $1300"; 20 min drive to Pechanga
4 Bed/2bath 8 person capacity Nightly rate $210-275 5 nights (12-17)= $1545.50 Deposit $200
#365547 Anza House 4/2 (1K,2Q,2twin,1portable) capacity 10 nightly $265-295 11 min drive 5 nights (12-17)= $1709 Deposit: $300 guests >8 $15+tax ea, extra BR $40+tax
#319632 "Beautiful Estate Overlooking Vineyards - Special Rate" 4bed/3bath capacity 11 Nightly $345 17 min 5 nights (12-17)$1895 Deposit: $500
Air BnB
https://www.airbnb.ca/rooms/403170 "Avocado house" 1bed/1bath capacity 2 22 min drive 5 nights (12-17) = $499
FlipKey
#p436341 Seclusive pool getaway 3bed/3bath capacity 6 5 nights (12-17) =$1371 deposit: $383
No idea if these are still available but if it saves anyone legwork that's already been done, all the better!
Good luck.