Who makes Robot figures?

[bishop odo]

Blue Moon has some:
https://www.bluemoonmanufacturing.com/view_product.php?product=BMM144

Reaper has a few in the Chronoscope line:
https://www.reapermini.com/FigureFinder#detail/50164

Wotc Has a few Star Wars that are not really Iconic you could use parts of?

[bandit86]

Zombiesmith has a few
http://www.zombiesmith.com/collections/a7-d12-airlock-7-docking-lvl-12

[n815e]

http://www.scotiagrendel.com/Products/index.php?main_page=index&cPath=59_66&zenid=5b1556d2c2fbadc0370bff9de6ea3d7f

http://www.urbanwarthegame.com/store.php

[Inso]

To echo Bandit86, Zombiesmith also have the Warpods:

http://www.zombiesmith.com/collections/warpod

[Elbows]

For bits, may I also throw out the old Mechwarrior: Dark Age (I think) clicks game?  Heaps of them probably cheap somewhere.  While they're probably slightly bendy-plastic, the range was pretty extensive, might be a good idea simply for bits and pieces.

http://www.ebay.com/itm/OEJ-MechWarrior-Dark-Age-LOT-Agro-Mining-Mechs-Demon-Tanks-ConstructionMechs-/361371567266?hash=item54236c84a2

^Stuff like this perhaps?  I see a heap of launchers, weapons, tools, maybe some cockpits you can separate etc.  I don't know the full scale, I think they're maybe 15mm appropriate?