Air cleaner case for '81 305

I posted this request in wanted, but figured I would try here too. I bought my first bike a few weeks ago and have been trying to diagnose hard starting and idle issues. Pulling off the seat I discovered that the filter and cap are missing! I've sourced a filter and mounting hardware from Babbitt's, but can't find the obsolete cap, new or used, anywhere. Before I craft something shoddy of my own I thought I would look here on the off chance someone has a box full of KZ305 parts somewhere.

Thanks for being here!
Chris