What kind of models are you asking about Yegbey? If you're talking about plastic model kits such as those manufactured by Revell, Hasegawa, Airfix, etc., there are a couple of good sources:
There are others of course, but the above three have a very wide assortment of kits, good prices, and are owned by very friendly and knowledgeable folks. eBay is not necessarily the best place to look for these kind of kits. Sometimes you get very good deals on eBay, but I've also seen some kits sold for far more than they're really worth. One good thing about eBay is that you can often find old, out of production kits.
For r/c models you can also try:
Hope this helps