If it's minimal maintenance you're after, these quality PVC belts with impregnated lubrication require less attention to make things run smoothly.
This Sportsmith treadmill running belt fits various StarTrac* treadmills
Fits E-TR9001

Fits E-TR9002
Fits E-TR9003
Fits E-TR9021
Fits E-TR9022
Fits E-TR9023
Fits E-TR9031
Fits E-TR9032
Fits Pro Tread 5500
Fits Pro Tread 5600
Fits Pro Tread 6500
Fits Pro Tread 6600
Fits Pro Tread 7500
Fits Pro Tread 7600
Fits Pro Tread 7700
Fits S-TRc3561
Fits S-TRc3562
Fits S-TRc3563
Fits S-TRC3581
Fits S-TRC3582
Fits Treadmill 2000
Fits Treadmill 3000
Fits Treadmill 3500
Fits Treadmill 3900
Fits Treadmill 4000
Fits Treadmill 4200 Sport
Fits Treadmill 4500

User facing surface: Black Diamond