Reloading is the only ong-term answer
Fairly cheap, accurate ammo? For 8x57IS? You have a problem.
Get yourself a Swiss rifle in 7.5x55. The Swiss surplus ammo costs 30-40 euros/100, depending on quantity, and produces unbeatable accuracy.
However, that does not solve your Kar98k problem. You will have to reload, as I do for every one of my rifles apart from the Swiss. And even then, you will not get much better than about 3" groups at 100 yards, unless you fit a scope. The Mauser open sights, which are no better for the 98k than for the M1871 (yes, the foresight blades even fit!) will limit the achievable accuracy, regardless of ammo quality.
Patrick