There are ‘authorised resellers of official bulbs that manufacturers list on their websites, but failing that, purchasing from a known reputable retailer would be my second choice to minimise risk. I’ve seen fakes up close and I know it would not be easy for a normal ‘Joe’ to spot.
It’s a possible cause of premature failure, poor performance apart from the usual issues of touching the bulbs with your skin that also cause early failure.
With anything, it will be down to the individual seller’s supplies. If too cheap be suspicious