British Star Wars Weekly #78

Kenner introduced the Imperial Troop Transporter in 1979.  It is the first Star Wars toy for the action figure line to not appear in a movie.  The original version of the toy had 6 electronic sounds and a later version, called the Imperial Cruiser, was released in 1980 as a Sears exclusive but did not contain the sounds.  The toy is shown in the mini-catalogs that were released with boxed Star Wars toys after it is released.  It first appears on the action figure packaging with the 31A cardback; the 31A cardback is the first version of the packaging that shows 31 Star Wars action figures on the back.  The description reads:

IMPERIAL TROOP TRANSPORTER

Replica of Imperial STORMTROOPERS "HOVERCRAFT" VEHICLE holds 11 Action Figures. 6 STAR WARS sounds: C-3PO, R2-D2, STORMTROOPER, and others. Front hatch opens. Manual rotating laser gun and swiveling radar disk. 6 side compartments hold prisoners. Action Figures, batteries not included.

While the text for this vehicle says the side compartments are for prisoners, most of the advertisement photos show Imperial Stormtroopers occupying those 6 side compartments.

The Imperial Troop Transporter appears in the stories for Star Wars #31 and #32.  Star Wars #32 is titled The Jawa Express for good reason; Luke Skywalker, Han Solo, Chewbacca, C-3PO, and R2-D2 hitch a ride on a Jawa Sandcrawler to escape from Imperial Stormtroopers.  We see Baron Orman Tagge and his brother Silas Tagge use a Troop Transporter to visit a successful demonstration of the Omega Frost weapon on another Sandcrawler and then use the Transporter's laser gun to destroy the frozen heap.  Towards the end of the tale, we get to see our heroes in a Sandcrawler take on several Troop Transporters.

Star Wars Weekly #78a - Marvel Comics, England (August 22, 1979)
last third of Star Wars #32

While the Imperial Troop Transporter is never shown on a U.S. cover, the vehicle does appear on the cover of Star Wars Weekly #78.  In a scene not show inside the comic, Luke is standing on the Sandcrawler, wielding two pistols, and attacking a Transporter.  Two more Transporters are approaching in the background.