Emergency Mylar Thermal Blankets are not made to block RF radiation but they do a very good job doing just the exact thing. The Mylar blankets are a very cheep temporary solution when you are on the go, or when you want to test and see where and how you need to use protection (as a debug tool).
They can be found on amazon
Pack of 10 for 8.88 - http://amzn.to/2ezMMFq
Pack of 20 for 12.99 - http://amzn.to/2fyH4Z4
Pack of 4 for 4.75 - http://amzn.to/2eIgNq4