Russia would be their best bet but it seems as though Russia shifted from "We'll give Maduro oreshniks if you don't back off" to "Ehhh, go right ahead" and I'd like to understand why. Some people are saying that there was horse trading going on, where there was a backroom agreement thar the US could have its Donroe Doctrine in return for leaving Ukraine to its own devices but I don't know the truth of it.
That leaves China's air defence systems, but I'm not sure that they're well tested in the field and I'm not sure if they're cutting edge, or Israel/the US.
Maybe in a different timeline Russia might have okayed transfer from Syria to Venezuela but that is not to be.
By this point things are far too late anyway. If there was some really cutting edge autonomous air defence systems that Venezuela could manufacture munitions for domestically then it would be different, but that's an absurdly tall order. Otherwise it would require building up the back end support like radar, training the military in its use, and having a steady supply coming via shipment. The US would knock out radar, any permanent installations, and they'd blockade arms shipments and the lead-in time before it would be possible to have an effective modern air defence capable of holding out against the US would take months and months, if not years.
Drones could have levelled the playing field quite a lot but that still takes a lot of training and it would be hard for Venezuela to get enough or otherwise it probably would have been down to using stingers or something more modern but honesty I think the ship sailed on this one, unless there's major changes to their situation. Also note that the best air defence is only useful if the military uses it and to seems like the Venezuelan military barely fired a single shot so...
