As Scott said, the 1.25" eyepiece is the most common and is standard across most telescopes.
But also note that there are some eyepieces of 2" and some of .96" but these are not so common, especially among current starter scopes.
The good news is you can pick up 1.25 plossl eyepieces fairly easily, some camera shops may even carry a small range. Australian geographic has some too, although these may be more expensive.
Also, most scopes come with two standard of reasonable quality, and as people upgrade they may not use these anymore.
I have a spare 25mm eyepiece that I can give you if you PM me your address. But there are probably people closer that can let you have one or two.
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and Merry Christmas
