Not legal advice: Infrared Pass Filter (IPF) is a special optic that will let you to penetrate an object and view what is underneath it.
The military has used Infrared night vision equipment since its development. In the 1960's there were a large number of "sniper scope" IR devices available and in the 1990's and 2000's there were a number of M18 IR binoculars offered on the market.
See this vintage M18 IR binocular from eBay.
While binoculars that you can find online with this feature are difficult to find, or are not marketed to provide this ability, you can look for stores that sell "night vision" products like OpticsPlanet.com – that has one the largest collections of "night vision" products.
Meanwhile, others have developed an alternative way to introduce this "see-through" technology. Advanced Intelligence introduced their X-Reflect X-ray Vision Glasses that has the ability to see through some type of clothing material (mostly swimwear and many types of synthetic materials), most dark windows even through dark sunglasses and works indoors or outdoors.
The IPF itself cannot penetrate an object's surface, however when used with Sony Camcorders with Night Shot Function, you will see for yourself, the real power of the IPF.
But Sony, who discovered the cameras' X-ray ability immediately changed the way it manufactured its Nightvision cameras so they would not allow users to peer through clothes. Legal authorities say using them for voyeuristic purposes could carry criminal penalties.
Tips! Read this awesome guide on How To Choose the Best Binoculars at Optics Planet.