Murfee

I just bought a 1974 DT125 Enduro with 3.00x19 front and 3.25x18 rear tires. It's in great shape but the tires (dated 1993) are dry and cracked. My first try at orderiing tires did'y come up with stock sizes so I might have to go one size up. I don't have a manual yet. Can anyone tell me the rim sizes on this bike and does anyone know where I can buy new Trials tires in this size? I want to keep the bike stock an ride it. Thanks