My first thought was metamaterial cloaking. Interestingly, metamaterial cloaking is mentioned in the Cloaking Device link in the question.
If you've done a highschool science course, you should be vaguely familiar with the wave-properties of light. This is what what allows a prism to split a white light into a rainbow.
Prisms have their limitations, so higher-levels of science often refer to things called Diffraction Gratings when teaching optics and quantum mechanics. They're cheap, reliable, and can be manufactured with very specific properties. The property most commonly sort after is the slit size - the size of the gaps in the grating. Different sized slits will bend different colours of light to different degrees. The angle the light hits the grating is also key, but that's a simple matter of just shining your light at the correct angle in the first place. :P
There is a downside to all of this; your grating's properties are fixed. One grating may be useful in one experiment, but useless in another. This makes diffraction gratings a pretty poor candidate for a high-tech cloaking device.
- We want to be in control of spacing between gratings,
- and we want to control the angle light hits the grating.
Lets turn the first problem on its head: instead of moving the gratings closer or further apart, let's make them bigger or smaller. This is good, but we still have the problem that Mr. Secret Agent is only invisible when people are looking at him from very specific angles!
We solve the second problem by being able to point these in the direction of our choosing. And this is made more difficult by the fact that suits change shape. They bend and deflect as you move about in them. Not only do we have to align the gratings correctly, we have to re-align them every time we do something!
Why don't we create a grating out of hair-like structures? Maybe ones that you can control the angle of? If we turn to the science books, we see that nature has something that almost fits this bill!
Mr. Secret Agent's cloak is going to have a thin layer of hair on it. I lie! These hairs are actually thin sheets, say made from graphene, rolled into tubes. Picture a sheet of paper rolled up into a tube. How tightly you roll the tube will determine how big or small it is. At the base of the tube is a Kinetosome - what's effectively the world's smallest biological electric motor. Use this to wind and un-wind the roll. This is your spacing problem solved. More Kinetosomes, artificial muscles, or maybe piezo-electric actuators, point the hairs in the directions of your choosing.
Which leaves one final problem: choosing the correct direction at any point in time.
I'm afraid there's no amazing futuristic science involved in this step. It's just mathematics. Very complicated mathematics, but ones that we understand today. You may need to integrate a small supercomputer into your suit, but given that Moore's Law still holds, and most major semiconductor manufacturers are working towards miniaturising their stuff, it's no stretch of the imagination to have this available (at great expense) to a government-funded R&D engineering team.
Just a side note, these hairs, no matter what they're made of, are most likely not going to like fire or being in contact with hot things. A gust of wind is going to be an annoyance too.
Heat emissions. Solve this by coating the inner lining of the suit with Peltier Coolers. It'll get nice and toasty for Mr. Secret Agent, but he comes from a tropical environment and handle a little heat just fine. The limit to the system is going to be how hot Mr Secret Agent is, and how much power is available to pump the heat back as it dissipates. If the operator is climbing about, hanging from the ceiling, stealing things, and being a general nuisance, the suit can operate for about fifteen minutes.
If the operator sits perfectly still, and remains calm, it's perfectly reasonable to think the suit could operate for a few hours. Maybe even an entire night if the wearer lies and down and has a sleep.
Nothing here really weighs that much. The cloak, in theory, could operate equally well on non-visible spectrums of light... though probably not at the same time as visible light. There's very little in the way of moving parts, so the noisiest thing is going to be Mr. Secret Agent's mobile phone if he forgets to put it on silent.