It is in the shop but you can't use them if you're not on the 2nd difficult fight with Kama because until then the effects dont apply

When Kama sends you to space there's the fight with her

Then 4 cutscenes

Then the fight with her where the bar is in effect and when you can use the tickets

Oooooh. I didn't realise there were 2 fights. I just read that you only have to get the first health bar down on the first one. Am dumb. Thank you very much! 😊

On the 2nd fight the shop will open and u use the white ones to lower the bar so that she gets weaker.. but theres black ones so u can increase the bar again and see if u can go against a stronger version..