A Beck speedster recently sold on BaT:
https://bringatrailer.com/list...06-beck-speedster-2/
This one we are all quite familiar with:
https://bringatrailer.com/list...he-356a-speedster-5/
This Beck was at auction the beginning on the year:
https://bringatrailer.com/list...-2015-factory-build/
....another Beck in October 2017:
https://bringatrailer.com/list...2006-beck-speedster/
That said, it doesn't appear that many were available prior to 2017. Maybe BaT changed recently?