I know what you mean. Thing is, normal people simply don't know about fake cards. They find out the hard way, like you and I.
Obvious fakes - yeah, and those 256GB SDHC cards. Haha! The SDHC spec doesn't go beyond 32GB!
I have bought second-hard cards from ebay with some success but you have to sniff out the sellers who sound like they know what they're talking about e.g. state where they bought the card originally; tested with h2testw; how old it is etc. However, with the price of new cards falling I don't bother doing this any more.
Places to shop : MyMemory is one of my faves at the moment. Their own brand cards are good value. I've got one of their 512GB uSDXC cards in an iPod right now.
If you want a named brand then you could check their websites for authorised sellers e.g Sandisk
https://shop.westerndigital.com/en-gb/distributors
MyMemory, PicStop, loads of others listed there.