Chasing a Dual Slide Harmonica

Hi

Im looking into this for a good friend of mine who has been chasing a Hohner double slide harmonica for a long time.
He’s 58 now and back in the day his Opa used to play a Hohner double slide harmonica.
All attempts to find something like this have failed thus far and sadly Opa took the Harp to his grave unfortunately…

Can anyone point me in the direction of a dual slide Hohner ? From his rough description it was allot bigger than a standard blues harp and the slides did something likie changing the key major or minor. He used to play jazz, dutch polka, some swing and blues. By all accounts it was apparently a very versatile Harp.
Sorry if this is quite vague i am a guitarist and have no idea where to start but all indications thus far is that they arent made anymore but if i can at least get an idea of what it was could maybe source one second hand.

Any help would be greatly appreciated.

D