You literally can buy stablecoins almost anywhere that has bitcoin listed, and as I know there are tons of exchanges that support credit cards which you can use them to buy almost all cryptocurrencies.
But the problem is if you want to use a stable coin then why not just use cash since stable coins are just coins/tokens that are pegged to US dollar, however there are ways to make an algorithmic coin/token that stays in the same value with minimal volatility and change in price(not more than 5%) I would probably use them since there are some ideas and innovations behind it and they're not just some ordinary coins and tokens that are backed fully/partially by actual Fiat.
I do not get why people do not use those algo coins, and why those algo coins are not keeping up with their own created system. Look at bdollar these days, it suppose to be 1 dollar pegged but it is now at around 0.6 cents and that's why the sbdo dropped from 8300 dollars to 1400 dollars as well, everyone is bleeding out money there right now.
The whole point is that, as long as there are buyers the system goes on, let's say there are not enough buyers? In that case bond starts to work and you make 10%+ more profit thanks to that when it goes back above 1 dollar. But right now it is not working, even bonds are not fully sold right now, which I assume will be soon but it is not doing good anyway.
I think it is obvious that people are not fine with constantly growing interest and see that as impossible. I think it is quite obvious that it will go back above 1 dollar because more and more bdo is burned, but that is going to take some time and showed the problem with the system.