Photoplethysmograph - Pulse Oximeter

Hello
I'm developing a photoplethysmograph(PPG). It is very similar to pulse oximeter, but use only the infra red led.
I would buy a finger clip probe that i can use in my project. At this moment i'm using a simple IR led and phototransistor for acquire my photoplethysmograph signal but i have very problems. This problems are mainly the finger position and his small move and the light.
I have searched the finger clip probes but they are very expensive and i'm not secure that i can use in my project. Indeed, many of this haven't a public schematic or a datasheet.
Can you suggest me a probe to use in my project? I can buy also a finger clip probe for pulse oximeter(there are two led, i can use only IrLed).
I hope you can help me to find this probe.

Thank you
Best regards
RM

maybe this will help. check google should get you started.

**broken link removed**

HOA1397-001
HOA1397-002
HOA1397-031
HOA1397-032

try to use those infrared reflective sensor. l had try one and its working but l forget the model code