You love - like me - the battery / vertical grip of your modern analog or digital SLR?
And now you wants one for your old mechanical SLR?
No problem, it's very easy to build a home made vertical handgrip.
I've built one for my old and heavy Porst FX4 (Praktica Nova 1b).
I've used the handlebar of my old and broken Flymo L470 petrol hover lawnmower.
The end caps are from Fuji film boxes.
The cable release is optional at the Praktica, 'cause the shutter release is at the front and not at the top. You can adjust the lens with the left hand and with the forefinger you can trigger the shutter release.
Certainly you can also install the cable release inside the grip.
It works very good.
EDIT 18.03.11 - 20.45:
Just a cosmetic update. I've changed the shims, now I've used shims of a mountain bike brake booster.