First, a nit-pick:
The recoil lug is the projection on the bottom of the receiver that engages the recoil shoulder on the stock. That area of the stock behind the recoil shoulder is called the recoil shield.
Now, on with the show.
The stock crossbolt found in all K98 rifles (not sure about Gewehr 1898 rifles) is there to give the recoil lug a solid point to bed against and to spread the impact of recoil out over a larger area. Due to the widely varying quality of wood used from WW1 on, the recoil shoulder was reinforced with the stock crossbolt to prevent the stock splitting or the recoil shoulder being split out (which is fairly common on civilian 98s made just before and just after WW2).
As far as finding a stock, you can buy a stock from Boyd's stocks, or buy a semi-finished stock from Richards MicroFit. It will cost you about the same and look much better than a sporterized piece of 100 year old walnut. Or, if you just gotta have a military stock, PM me for a Spanish FR8 stock.