The sound is very basic and very easy to recreate on almost any synth that has a sine wave LFO, 12Db lowpass filters and at least PWM or a hard sync.
If you're after true analog, the closest thing to a 2600 would be an ARP Odyssey. Look on e-bay, they go for about $200 to $400 US.
If you're opwn to digital, then try GMedia Ossity, which is a software version of an Odyssey. It's very good.
On a hardware side, synths like NORD lead, NORD modular, Novation Supernove or NOVA, Korg prophecy, KOrg MS2000 etc.
Basically any virtual analog synth.
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