[mike777]

This simple idea sounds so old that it is new.
Below is from a Bob Hamman quote in a bridge article.

1NT=P=2C=X
2D=Diamond suit and denies 4 card major
pass=denies d suit and 4 card major.

Same is true over a 2nt opening bid.

[Gerben42]

I prefer something different. Partner usually doesn't care about ♦, so you play TRANSFERS here.

1NT p 2♣ X ?

XX = good ♣
Pass = no 4M no good ♣
2♦ = 4♥
2♥ = 4♠

This will usually put doubler on opening lead against a major suit contract.