You can constantly replay the first level of this game to get the two Mutators you need. it is by far easier to juggle the multiball then to get lucky enough to get a multiball while Fastball is in play. This technique also works for Triple Threat achievement which requires getting a second Multiball while having two IonBall's in play.
Multiball Mutator looks like two IonBall's together, Fastball is the Yellow IonBall Mutator. You could also play the entire game then after finishing the final boss hit continue game and you restart on level one with all upgrades already purchased.
According to CasperTC you must have the multiball first, then get the fastball.
If you choose the game continue option DO NOT UPGRADE the IonBall! Focus on Mutator increases, paddle size, and the chance to avoid losing a life on dropping the IonBall.