Two thoughts -

1. Unfortunately, you are choosing to work somewhere where your work is "kept secret". In other companies, this might not be the case. You should consider this and how it may or may not affect your future job opportunities.

2. Is it possible to take chunks of your code and "scrub" them so they are not revealing anything proprietary by sharing? (still need permission of course) I do this on the business/prototyping side a lot, not sure if it transfers to the development side.