Try also to go to a Vet. A friend of mine had his Columbian Boa killed by a Vet. Allthough Tegus are considered omnivorous, they are definitly more carnivorous. The main diet consists of rodents and larger insects. Feeder Gold Fish are another good variation to the diet, and should be placed in a shallow dish to ease the catching of the prey.
Eggs are another favorite.
To prevent salmonella, the egg should be almost hardboiled and then cooled down to prevent injury to the animal. Sprinkle a little vitamin and calcium powder on the chopped or stirred up egg, and your Tegu will be gratefull. I have heared stories of Tegus so obsessed with eggs that their owners had to dip everything in eggs inorder to make them eat it. This is definitly not the norm though. Lean strips of beef can be offered also every once in awhile as a treat, and will be readily devoured.