You cant buy a phone on eBay that will work with a kosher sim card.
Unless you bring it to a store and have them "make it kosher for you"
Most Samsung devices, zte z223, the new Att lg b470 are some of the inexpensive models that are kosherizable
(love the word )
You can pm me when you get to Israel is you want them kosherized. Cost between 50 and 100 shekel depending on model