steaming pump parts in avent?

I just bought my pump last night for use of building up a stash for late fussy nights (have same problem as pp with late evening/early morning feedings when DD is just frustrated and hungry) but was wondering if I need to buy the microwave steam bags by Medela specifically or if I can just steam the parts in my avent microwavable bottle steralizer? Anyone know the answer or have you done this?

TIA