I am with you. The auto part stores carry many oem equivalent parts now. I recently purchased some coolant hoses and they are probably just as good as the oem ones except they are probably 20% cheaper.
That said regarding parts I've happily used aftermarket parts. I went to AutoZone and O'Reilly's websites and both have the two belts readily available in a local stores to me. (And some have 3 year warranties, unusually long considering they are rubber items, Continental at AutoZone and Gates at O'Reilly's).