But there are very few other options for custom belt pulleys.
Also, you need to make sure, when changing belt gearing, that the combination of pulleys and belt length is within range of adjustment of your dropouts. There's a calculator thingy on the Gates website.
Phil Wood belt pulleys can be ordered from Hubjub. (Not listed, but available as special orders... http://www.hubjub.co.uk/philwood/philwood.htm)
They are expensive.
And very heavy.
But there are very few other options for custom belt pulleys.
Also, you need to make sure, when changing belt gearing, that the combination of pulleys and belt length is within range of adjustment of your dropouts. There's a calculator thingy on the Gates website.