He seemed embarrassed to purchase a hair growth product, so I pretended to buy it for myself, took it to the cashier, and bought it for him.
こんにちは！
ご質問ありがとうございます。
ご質問について、いくつか言い方が考えられますが、例えば、
He seemed embarrassed to purchase a hair growth product, so I pretended to buy it for myself, took it to the cashier, and bought it for him.
とすると、『彼が育毛剤を買うのを恥ずかしそうにしていたので、私が自分用に買うふりをして、レジに持っていき、彼に買ってあげた。』となります。
役に立ちそうな単語とフレーズ
pretend ～のふりをする
参考になれば幸いです。
I pretended to buy a hair growth product for myself when it was actually for my friend.
"私が育毛剤を買うふりをして友達に買ってあげた"
- I pretended to buy a hair growth product for myself when it was actually for my friend.
「彼が育毛剤を買うのを恥ずかしそうにしているので、私が買うふりをして、レジに持っていき、買ってあげた」
- He seemed embarrassed to buy a hair growth product himself, so I pretended to buy it for myself. I brought it to the cashier and I bought it for him.
日本 
アメリカ合衆国 
