I recently went through a similar scare with my beardie, so i can try to help you out.
There are a couple of ways to get through this 1. the natural way or 2. surgery.
You say he hasnt defecated in a week and looks bloated, was it one week ago that he ate the plastic? Also, is he still eating?
As long as he is still eating you have a few days to work with, ideally you should start at home treatments the day it happened to increase chances of success, but you can still try.
If he is eating...
Give him warm water soaks 1-3times daily for 30-45minutes, the extra hydration will help lubricate his system and help him to pass the plastic. You can gently massage the belly while you are soaking him to help work everything down. Feeding foods that are natural laxatives such as squash and pumkin can also help. If he is agreeable enough you can also give him some mineral oil with a syringe. If this doesn't work after a couple days, go to a vet.
If he isn't eating...
Go to a vet asap. If he is bloated and not eating then the plastic is probably blocking him. A good herp vet will be able to take x-rays to see where the blockage is and will be able to preform surgery to have it removed. A vet will also be able to go over all your options with you, including tips for at home treatment.
Good luck!
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0.1 Bearded dragon (Hannabil)
0.1 mexican Black kingsnake (Morticia)
1.1.2 Leopard Gecko's (Pogo, Louise, Orion, Jeffrey Nothing)
0.0.1 Tokay Gecko
1.0 Blue Tongue Skink
0.0.1 Reverse Okeetee Corn (Autumn)
0.1 Bullmastiff (Asha)
4.1 Cats (Poe, Tucker, Abhid, Felicity, Emmy)