You have a few options:
If you find a BMW dealer ... or a good MC shop, you may find a new or used shock that will work ... part exchange for your blown shock.
AFAIK, the "Original" BMW shock on your bike is most likely a low spec Showa ... if not then it's a low spec WP. BMW use both ... and neither are the best that WP or Showa make.
And ... if a Showa unit ... they can be rebuilt ... if you know how. Bit of a job breaking it apart but can be done ... by a Pro. Not sure on the WP, but most any shock can be repaired/re-valved by a shock pro.
But you won't likely find a suspension Pro where you are. But if you can find a decent shock that fits ... and does not leak ... use it! Even if the spring rate is wrong ... just swap over your spring from your old shock. The length is important and location of the eye holes ... and it must also not be too fat.
Or, if you find a BMW dealer, maybe they'll remove a NEW shock from a bike on the floor and sell you that one? ... taking your old shock until a new one arrives from Germany. Worth a try anyway.
BMW dealers here in San Francisco Bay Area have loads of stock WP shocks off of BMW R12GS's. Dozens of them tossed in a corner, most with under 5000 miles and for sale very very cheap!
Most Beemer guys immediately upgrade to an Ohlins, ($1000 option, front and rear on the GS!) IMO, the stock WP is not that bad, but the damping does fade after hard riding loaded up after a year or so.
Your shock will not have any branding on it. You just have to know ... or go onto a GS 700 Twin forum and find out.
Good luck. You can ride the bike but soon you will have NO DAMPING, only spring. Use caution, make sure shock oil does not get onto rear tire.