Don't understand why the question about "who manufactured the MANPAD?" is so important. As correctly mentioned above, there is quite a considerable black market for such devices accesible for all "bad guys". Could be Russian "Igla" taken from or lost (or even sold) by the Assad's regime or moved from Lybia, could be US ones moved from Iraq, could be Chinese, whatever. It is also clear that any modern MANPAD can easily reach such an aircraft as Su-25 at the altitude it was flying, especially as it did not maneuver and not used flares.
Just take into account that jihaddists in Syria now do have these toys and act accordingly.