Interesting intellectual question posed, Sarmad.
Personally speaking, I'd be more inclined towards you NOT doing something of that sort (at least not permanently), for the simple reason that it seems to be (at the very best) a stop-gap arrangement. The 90 Series is pretty much a staple SUV in Pakistan, so I don't really see a huge problem in you getting a new left hand spring. Moreover, in today's "global village" parts that aren't readily available locally, can be procured from elsewhere. Add to this, the fact that, within the country we have several markets where there's a plethora of second hand parts for the Series 90 (City Sadar Road, Astabal, Sultan Ka Khu, Mithu Khan ka Ahata {in Pindi}, Bilal Ganj {Lahore}, and Shuba and Tahkaal {Peshawar} immediately spring to mind).
Of course, the possibility of the Left Hand Coil Spring for the Series 90 being a completely KKG part that isn't available ANYWHERE, can't really be ruled out. In which case, a permanent weight (like 2 cubic feet of lead) should be able to provide some ballast. Which is STILL not recommended, seeing as how we're environmentally friendly people...and lead poisoning can be a nasty thing.
If you need help sourcing the required part, you're more than welcome to any help I might be able to render.