Go buy the LF version of your PIC.

The LF series work down to 2.0v so for 16F876 choose 16LF876.

Also, don't be afraid to use the 'A' version, there's usually only very minor differences (in the case of the 876A only two additional registers to handle CMCON and CVRCON between it and the older non-A version). You'll probably find the 'A' versions are cheaper too. I've not had any problems intergrating 'A' series parts into older non-A designs.