There are several sources for a VHS copy of "Barney: Waiting for Santa" including eBay, Amazon and Alibris. All three are online retailers that often offer used or hard-to-find merchandise.
"Barney: Waiting for Santa" was released on video in 1992 and 1993 and remained on sale until 1998. It was the fourth release in the "Barney and the Backyard Gang" series.
The price of a new or used copy of the film depends on the condition and availability at the time one places an order. As of 2015, the video is considered "out of print," meaning that no new copies are being produced.