The ability to sew an inertia-negating gadget into an uniform would seem to negate the need for rocket boots and make it unnecessary for our heroes to stay attached to the ground in any given situation. So we probably have to believe that such gadgetry in 23rd and even 24th century is of somewhat low performance, and better performance comes only from excessive bulk.
Actually, the rocket boots are proof, both of sufficient miniaturization of power sources and of inertial control to make some sort of battle armor perfectly feasible. It's not as if those boots were strapped with a pair or fuel tanks, after all, but they nevertheless were able to generate enough thrust to propel three grown men straight upwards at about one and a half gees. That means either the boots have small fusion reactors and impulse engines built into them -- which is slightly
absurd -- or they have an intake system that sucks in the outside air, superheats it and propels it downward to produce thrust. There's also the fact that the boots are self-balancing and don't even have to be pointed at the ground to provide lift, so there's almost certainly some sort of antigrav technology involved.
So, assuming Kirk and Spock and McCoy combined weight about 200kg (Spock was on a diet and Bones had become emaciated from eating beans all month), and assuming Enterprise' grav plating was set to a standard 1G, you have a device that can sustain just under 2000 newtons of force for long periods of time and surge to 3000 in short bursts. That's a useful power output of about 3kW squeezed into a pair of high-tech goulashes and a belt.
Don't really know the power capacity of Worf's communicator in "A fistful of Datas" but it couldn't have been THAT much greater than its 23rd century counterparts. That particular forcefield did everything you'd need it to do and more, the only limiting factor was the amount of time it could stay on. If you expand that communicator's power cell into a unit the size of, say, a wearable vest with field emitters integrated throughout, you could probably maintain that field for a good twenty minutes or so. OTOH, a purpose-built forcefield generator probably wouldn't run out of power until something hits it, in which case it should be able to pack enough juice to deflect at least a few dozen rounds of .30-6 or one direct hit from a phaser blast.