The plastic fastex buckle is broken? Or something else? Cheapest route is probably just replacing buckle. Anything else would probably require some work to get it attached to the Indian tank. The above posted eBay links are definitely great prices on some stuff you can make work. The liter strap with cobra buckle is a steal. I may even buy one.
ETA- looked at this a little more. Actually probably really easy upgrade if you buy the above linked items. Run the liter strap through the padded belt. May have to use some 550 cord to join the two ends, but that would be inside the padded belt. Then use one wrap through the molle straps around the plastic back plate. Gives you padding plus belt with cobra buckle.