Hi Nats, I bought a Doppler last year and I agree it does wonders for reassurance. I bought the Hi-Bebe , I managed to get it on Gumtree second had, you should look on there or Ebay.
What I will ay though is that I first used it last year at 14 weeks and found the heart beat. This time around I've stupidly been trying since 8 weeks and still cant find it but Im not worrying as I've had scans and all are fine.