Unless you've not turned the TV on for the last six months, you'll know that the Ukraine is in a state of some confusion, right now. The country is very split about its own future. This is MIGHT have an impact, somehere, on the chain of money/goods flowing from some parts of that country, to the West. I strongly recomend that you COMMUNICATE DIRECTLY with any supliers beforehand, to satisfy yourself that any transaction will not be impacted by the current sad events.
As otherwise noted elsewhere, look for ebayers with solid feedback scores, and a history of selling this type of product; check past sales of IN18 nixie tubes in particular. Look for phrases like "Date Matched" and "New, in box (NIB)" or "New Old Stock (NOS)". some ebayers will sell you unmatched, randomly dated and well-used tubes, without pointing this out (which is naughty...)