We aren't back in the day though dreaming about owning a Jupiter 8 or to achieve the exact sound of the original song? The guy asked about any free vst's available that he could approximate a "synth bass-like" sound. I made a suggestion for one that is quick and free to download, with an easy to use interface, also providing a quick demo of it. There you go , a suggestion as asked for?
And there are always solutions, for example:
1) Play the bassline on a real bass and mix in a synth sound underneath.
2) Open up another instance of VST, create another bass sound, play octave lower, detune and layer up the sound.
3) Spend a bit of money and get a Boss SYB pedal to get a true "bass synth" sound, then re sell it after project is finished.
4) Sell house, wait around for a "Jupiter 8" to become available (good luck) , and use proceeds to purchase.
If the project involves other musicians and therefore will be a mix of instruments, what point is there in creating a speaker-blowing bass sound that may seem great in isolation, but devastating to a band mix?