First, the ebay carburetors. The first one you cited, I would not buy, simply because the face of the carburetor body which has to clamp against the insulator (with a thin gasket in between) has been machined with a badly set up roughing cutter, and never finished. A manufacturer who would put a product like that up for sale might do anything, and is best avoided. The second one you cited looks similar to a Keihin such as Honda might use, but the seller asserts that it can be used on GXV120, GXV140, and GXV160, despite there being relevant differences from the original carburetors in the case of the GXV140 (unlike the GXV120 and GXV160, the 140 does not have an integral fuel on-off tap on the carburetor, but this one has such a tap). One of his illustrations shows a long choke lever arm supplied as a bonus, but I suspect the arm is actually only used on the horizontal crankshaft engines. So, one of the carburetors (the slightly cheaper one) is badly made, and the other is being sold by someone who may not know what he is talking about, or alternatively may have a loose grip on the truth. Neither of these issues would keep me from buying and using the carburetor if I didn't have a choice, but in your situation I'd begin by running through the standard carburetor cleaning and checking procedure on the carburetor you already have. If you find replaceable parts missing or damaged, you might try looking for overhaul kits on ebay, or sending a PM to roebuck.
I suggest that before you do anything else, you have a look at this video, which shows you how to clean your carburetor "the Honda way":
