What is the wavelength of an Itron C1S IR LED?
Measure the voltage drop across the junction. The band gap energy of the diode junction is also the energy of the photons in electron Volts (eV). Find the wavelength with $$\lambda =\frac{hc}{\mbox{E}}=\left( 4.1366\times 10_{eVs}^{-15\; } \right)\times \; \frac{\left( 3\times 10_{\frac{m}{s}}^{8} \right)}{measu\mbox{re}d\; voltage}$$ Multiply by by 1,000,000,000 or use 3x10^17 for nanometers. You can do this with red or green LEDs and a spectroscope to verify.

However, the IR recievers are pretty broad band and just about any will work.