MVS kits are harder to come by the day. King of Fighters '98 is one of the tougher ones to find, which I am also looking for. Kits are not impossible to find, just extremely tough. As for KOF2000, you can find those on Ebay from Mdgamesales.
Unless the person doesn't know anything about kits, you will be expected to pay more, which I have found out through collecting for the past few months.
I've always gone by the MVS price guide before, which didn't accurately measure the prices for MVS kits, because everyone who sold kits were selling way above the high cost. If it wasn't cash I gave up, it was tons of loose carts I sacrificed to get that nice looking carton box.

Well worth it though.