Bag for holding valuables on bike while parked? I ride regularly in the city with my a few valuables with me. My purse, phone, keys, company ID card etc. I hate having a bag on me while ride so I am looking for a solution to have these few items in a bike bag, but also have them safe if I stop somewhere to run into  a shop or a cafe for 15 minutes. 

My original idea was to look for a small saddle or top tube bag that is lockable and also safely locked to the frame, and I can simply leave it there. As it turns out there is no such thing! Or I just did not find it?

My second idea was to search for a similar bag, but which is easily detachable and I can take it with myself as a waist bag for example. Same story, I couldn't find anything like this on the market.

Do you know any bag that could work for me? Or do you have an alternate suggestion for my conundrum? 

Thank you very much if you take the time to answer! Ride safe!
János
Leaving valuables on the bike sounds like a very bad idea. Bike luggage just isn't going to be robust enough to resist theft if left unattended, and the whole bike itself may be vulnerable to theft.

What you want is a bag or caddy with a quick release so you can easily detach it and take it with you when you leave the bike. Many saddle bags have a quick release and come in a range of capacities.