Uy, I get it, doppler can be mahal talaga! Honestly, I'd suggest checking Facebook Marketplace or Carousell since maraming moms doon nag-sell ng baby stuff, especially sa Camanava area, you might find good deals from moms who've finished using theirs na. But just a heads up, pag secondhand doppler try mo makita kung gaano kalayo, kasi dapat accurate talaga yung readings, so baka worth it na i-save up for a new one or at least ma-verify muna ng seller na gumagana pa perfectly, okay?