Sterilising milk storage bottles

Hello mummies! I am currently using milk storage bags to store my expressed breastmilk and I’m thinking of switching to milk storage bottles instead as the bags are one-time use (quite wasteful) and expensive (I pump 8 times a day so 1 month’s worth of bags cost me over $30). But I noticed that most milk storage bottles like Autumnz are only PP material, and not PPSU or glass, which means I cannot use my UV steriliser to sterilise the milk storage bottles. How should I go about sterilising PP milk storage bottles then? TIA!