Yes, lots of authorized AND unauthorized issues for Ukraine. For example of the older Ukraine unauthorized issues, see this thread and the included links http://goscf.com/t/9611
In general, there have been quite a few bogus issues for many of the former soviet republics and regions. The recent Touva thread is another example. There are a couple of websites that do some basic documentation of bogus issues. I don't have the links saved on this computer. Maybe someone else has them, or you can do some googling with the keywords Russian Soviet former republics stamps bogus. There are also many many legitimate issues. But quite frankly, if it is being sold in a flea market type bourse... Even if they aren't genuine/official, even the bogus stamps are actually quite pretty. I don't mind having a few in my collection.
Safe travels! I hope the adoption goes smoothly! If you are worried about bogus issues, probably be safest to simply buy some modern stamps from the Ukrainian post office. Here in the US, modern Ukrainian stamps are harder to get; but most of the older Ukrainian stamps are pretty plentiful. Getting them in genuine used condition -- often much harder.