Patience
Seriously, be more patient in your search on Gunbroker. Yes, there are a ton of scalpers and overnight entrepreneurs on there, but you can find good deals on there, especially for something that is relatively common like an RC K98k.
Look for a good price, reasonable shipping quote, high feedback, and find yourself a dealer to do a transfer for you (if from out of state) for a good price (unless you are C&R holder).
But in addition to mp25ds4's suggestions, try AIMSurplus, Classic Arms, CDNN, AuctionArms (similar, but less crowded than GB), and SARCO.