They can force you to divulge your private key
No they can't. They can try but that isn't the same as actually forcing you. I've discussed this before but the blanket law re crypto keys in the UK pretty plainly isn't compatible with the charter. Also it's still a choice either way. If we all refuse to hand over keys the law is moot, terrorists won't do it so why should the rest of us; by definition that law is disproportionate. Hell this is exactly why the law isn't used because they don't want to see it tested because they know it will fail in both primary and secondary aim.
Now, where can I get one of these for Parliment?
Depending on your political flavour either Watson or Davis is probably about as close as you get.