Sand is their substrate, they live to dig. I've found that more sand - say, 3" deep - keeps them busier and happier. Even though they jump around to spots all over the tank they're still a bottom dweller. A tall tank would be wasted unless you're going to try to have fish in there.
Fish--we bought a dozen small goldfish for our blue as company/hunting practice/meal-on-the-hoof, in that order. It worked out exactly as planned. Every few weeks when he needed an extra protein boost he'd hunt down a fish. This despite his usual diet of Crab Cuisine, peas, carrots, blanched zucchini, an occasional chunk of defrosted shrimp, and algae tabs (his "cookie"--they spin it around, nibbling the edges).
No matter how adorable, they are killers. And that goes for the human fingers dipping in to add or remove things.
It's important to have lid on the tank. None of mine have been jumpers but there are others on this site who've had them. The last thing you want to hear is a sickening crunch in the middle of the night when you get up and inadvertently find that he took an exploratory flying leap.
You haven't mentioned what size your tank is but 10g is about the smallest for one...actually, 20g is much better considering you'll have stuff in there. And they do need the stuff, for hiding, exploring, staying interested in life. More than one, a bigger tank would be better and reduce the chances of them fighting and wounding or killing each other. Consider that they molt (moult?-sp) every 6-8 weeks until adulthood at 1-1/2 years old. They'll be fully 6" big as adults. How well will one fit in your space adulthood? Two?
When they molt they dig down and hide for anywhere from half a day to a day. They back out of their old body like a car out of the garage and lay low for a few days, weak and recovering. Then they're ravenous.They eat the old exoskeleton so don't remove it - they need the calcium, protein, minerals to grow that bigger body you'll see in a few days. If you get a chance to spot the exoskeleton before they polish it off, it's quite amazing. Absolutely perfect replica, down to their tiny legs. There are some videos on YouTube that people took of their cray in the process.
If you decide to add a snail or two (nerite for cleaning, mystery for fun) your blue or orange will kill and eat them. A less aggressive type (like Cherax Thunderbolt) will live compatibly with snails. I once watched my blue headlock, repeatedly punch, and finally suck a mystery snail out of its shell. I am not kidding. It was pretty horrifying to watch. Okay, no more snails for you, buddy.
The big-box stores have crays in a hit-or-miss fashion. They might go months without any. Local fish stores, if you have them where you are, may be easier as well as needing your business. They could at least ask their suppliers and maybe put in a order for you.
If you're not having any luck, Aquatic Arts (aquaticarts.com) sells wonderful crays of many varieties and ages. And prices. They are a small local business, just in someone else's locale. That's where we got our Thunderbolt. They really care about their crustaceans; great people and they answer all questions cheerfully. Their little guys arrive ASAP and are healthy, waving hello with those big claws as soon as you open the box.
Lastly, crawfish (as we call them in Louisiana) will eat every live plant in an aquarium. So plastic and silk are the way to go.