Spend the money you save by disregarding DVD-RAM cartridges on air purifiers and dust absorbers. Just kidding.
In addition to Hitachi's Maxell and Matsushita's Panasonic DVD-RAM media, there are Mitsubishi (up to 5x DVD-RAM as well), TDK, some more. There are also Ritek and Optodisc DVD-RAM media if you want cheaper ones (that I myself would never buy.)
TDK, Mitsubishi, BeAll (of Matsushita OEM), respectively, pictures from dvdnawa.com (of South Korea so don't bother to order from them.)
Melody of Taiwan (and also of South Korea) sells DVD-RAM media probably Optodisc OEM, not sure about that.
Double-sided 9.4GB 3x of Melody brand... costs 14,000 Won whereas Mitsubishi single-sided 4.7GB 5x of Mitsubishi brand costs 9,000 Won, easy choice.