You can buy them from eBay, but weve always found TCGPlayer, while still eBay-owned, to be the most secure and trustworthy way to nab Secret Lair drops post-release
And secondly, Ureni generates value as soon as they enter, and it only gets worse if they're allowed to attack
These days, Wizards of the Coast doesnt publically reveal information about how many copies of each card are printed
Also remember that if the card really has a problem and can't be used, it's the owner's responsibility to find a replacement to use in the event (or, if you can't or don't want to, exchange the card for one of the five basic lands to your choice, for the rest of the tournament)
Its still a respectable card in casual EDH decks and some Peasant Cubes