For the latest OS/BSP, please see our Topcon Software downloads page here in Freshdesk:
https://stwtechnic.freshdesk.com/a/solutions/articles/6000220237
If you need an older BSP/PClient, they can be found either in the Projektor Tool zip package (older releases up to ~2018), or can be generated from within the installed Projektor Tool (newer releases ~2019+).
You can also create a support ticket here in Freshdesk and we can help you get specific versions, if needed.