You could use a D20 instead, and re-roll if you get a repeat.
Using this method would mean you can't draw 0 (The Fool) or 21 (The World). But that's okay because those cards are meant to be removed from the deck anyway. Let me know how it goes!
There's randomtarotcard.com but the issue is that you need to pull cards and then discard them as you proceed through the deck. Probably best to order a cheap deck if you want to play.
