Use this OnShape linked document to add parametric pulleys to your project. By default I use an inner hole diameter of 22.35 which is a very tight tolerance on the standard skateboard bearings.

https://cad.onshape.com/documents/75e8bf08d175f365f1e1bc8a/w/51e2a051d52fdd57c3bfea4e/e/487ab181ed8f8e0de65c9449?renderMode=0&rightPanel=configPanel&uiState=662bf9288357a43518936265

A few sample STLs are available for download here..

Print in something strong, at least PETG, 4+ walls and 25%+ infill.