Is there such a thing?

Yes there is. Some people with the larger scale tanks (1/6 or 1/8 scale) have been equipped with petrol? type combustion engines.

Some of these tanks even use a 9mm blank fire pistol for the main gun sound.

Check out the UKTC (United Kingdom Tank Club):

http://uktankclub.star-one.co.uk/default1.htm

Cheers
Eric Scott