Peer pressure gets bored fast when your answer is boring and the same every time.

Pressure runs on the hope that you will move. A fresh excuse every time is a door left slightly open, so people keep knocking to find out which version of no is the soft one. The same flat answer, delivered the same way, is dull to push against, and most people give up sooner than you would expect.

Choose your line now, while nothing is happening. Short, repeatable, nothing clever, something you can say three times without changing it. Then move the conversation to something else. Boredom does most of the work for you.