Mantic have two Dreadball teams that are comprised of robots:
The
Ro-Tek Brutes:
And the
Chromium Chargers:

Of these, the first team (the Ro-Tek Brutes) are a huge pile of mix-n-match parts, so that you can make lots of different configurations. The Chargers are more "human" in their form, but that may suit you better.
Two further comments on these:
(1) You can find them rather cheap if you shop around (lots of people offloading KS stuff for example)
(2) They are a hard PVC plastic rather than the usual hard Styrene plastic. This means that mould lines can be a tricky to remove neatly (possible, just a bit more work than usual), and that you will need superglue to stick 'em together.
Finally, note that Mantic's models are generally more 25mm than heroic 28mm scale.