You didnt ask for a brand name? Thats the least inoffensive thing you can di assumjng asking to smell like them isnt perceived as an insult per se

Just ask

What is your fragrance or what product do you use recommend?

Even if its different from their own secret brand, Be and look sincere in asking. I doubt they'll be too offended by asking their advice

Everyone fancies themself a curator of taste or that which is desirable