I asked my husband to look up the DNS for the old Polish calculator that has disappeared and he said it looks like it's lapsed and not been renewed so the web page has gone.
So he's put together a replacement for everyone. It's not fancy (he's a tech wizard but not a designer, he has others to do that for him), but it does the job and will stay live as long as we need it.
Let me know if you think anything is missing or if anything unexpected happens when you use it.
Is it possible to pin it to this forum so people can easily find it?