Anyone knows, is it possible to buy modern version of this sort of Foot Bass Accordion?

What you're probably looking for is a bass pedalboard for an organ or keyboard.

For example, Hammond-Suzuki offer 13-note (XPK100) and 20-note (XPK200) versions. These are MIDI controllers with pass-through, so they can be used to control any MIDI keyboard or synth module.

http://www.amazon.com/Hammond-XPK-100-1 ... 0002D05B4/

http://www.amazon.com/Hammond-XPK-200-2 ... B0056IBK0K

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Vivat diabolus in musica! MTGuru's (old) GG Clips / Blackbird Clips

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Harry Geuns is making something like this. He calls it a foot bass. See

http://www.bandoneon-maker.com/harrygeuns.htm

Great sound! but not cheap.