Leftist terrorists in Colombia have been desperately trying to buy shoulder fired surface-to-air missiles (SAMs). The most likely purchase would Russian SA-7s, which can be had for less than $20,000 each on the black market. The Colombian leftists (the FARC) have been getting chewed up by the army and police during the last five years because the government has a force of about a hundred aircraft (helicopters, prop-driven attack craft, jet fighter-bombers, electronic warfare and reconnaissance). The helicopters are easy targets for older SAMs like the SA-7. More advanced missiles, like the SA-14 or 18, cost upwards of $100,000 dollars each, but are even more effective against helicopters, and have a chance against fast moving jets (while coming in low to attack.)
The problem is, the black market for arms has been heavily infiltrated by American agents, especially since 911. For this reason, the arms merchants are unwilling to move SA-7 type weapons to terrorists. The reason is simple. If the missiles are used successfully, Americans will likely trace the weapon back to the source, and keep coming. Gunrunners are basically out to make money, not play hardball with U.S. counter-terrorism agencies. Nations that manufacture these low budget SAMs (Russia, China) do not want a spat with the U.S. over this, and warn their customers that there will be repercussions if the missiles fall into the wrong hands, and the Americans come looking for suppliers.
But there are sources for these missiles. At least according to a sting run by American agents in Honduras recently. Hearing that there was a Syrian in the area offering to supply weapons, the Americans, playing the role (convincingly, apparently) of FARC weapons buyers, met with the Syrian, and were told that Hezbollah (the Lebanese terror group sponsored by Iran) had a weapons warehouse in Mexico, from which FARC could buy assault rifles, grenades, explosives, ammo and 17 SA-7s. Iran manufactures the Misagh series of SAMs, based on Chinese models, and one of them is basically a SA-7 clone. Iran supplies Hezbollah. The Syrian arms salesman was arrested in Honduras and extradited to the United States, but it's unclear if he has revealed, or even knew, the location of the Hezbollah warehouse in Mexico.
The Syrian wanted to trade a shipping container full of weapons for a ton of cocaine. FARC would have needed more ten times as many SAMs as the Syrian was offering, to change their battlefield fortunes in Colombia. But if the Syrian was telling the truth, 17 SAMs would have been a start.