Here is a selection of tanks from Tamiya with direct links to amazon.com if you are interested in buying one. I have looked into the 1/35 and 1/48 models but bigger and smaller models are also available. I chose models where the shipping is free whenever possible.
Here is a selection of German 1/35 models:
and German 1/48 models:
Some American 1/35 models:
and American 1/48 models:
Some UK models. The first 2 are 1/35 and the 3 other are 1/48:
And here are 2 Russian 1/35, 2 Russian 1/48, and 1 1/35 Japanese model:
Enjoy!