Bitfinex sells it. Other shitcoin exchanges to. In terms of storage, it depends what chain USDT. I can tell you, you feel dirty going down that way because all those are shitcoin wallets and they all suck and USDT is a shitcoin on shitcoin chains. Mild exception is L-USDT using blockstream green wallet, that's kinda fine but other than that, bad UX, bad allaround ...

But considering that there's no liquidity for it anyway, all that is beside the point. Curious, do they use USDT in Costa Rica?