Im looking for a fetal doppler any good ones that are fairly cheap?

if you have bought one and it worked good please let me know how much you paid and what brand and where you got it please. also if you know of a brand that is really bad let me know so i don't get that one...lol i am 16 weeks pregnant and i just worry a lot because i have had a still birth and a miscarriage so i just want to make sure everything is going good! I know they sell heartbeat thing at babies r us but they don't work till you are into your 3 trimester. thank you for your help!!