Red filter options for Minox ML?

I recently acquired a (functioning!) Minox ML. I would like to use a red filter on it. Would options should I be looking for?

The Minox uses a slip or push on filter, I think a Series V or VI adaptor might work, you find them on Ebay, maybe someone is China is making new filters.

Measure the diameter of the lens and look for push-on filters of that size on eBay. If it's 31,5 mm, as I read on a forum, then a 32 mm filter can easily be made to fit. But then you would also want a sun shade of that size as well. If you are not going to use the filter that often, and you already have a red filter you can just hold it in front of the lens.