Yeah, the grot tanks are roughly the same size as Kanz (well, the hulls are larger, but the tanks don't have the big kan arms), so probably a bit too big to count-as something on a 40mm base. Meganobz would be a closer fit.
Kromlech do indeed have a wonderful selection of goblin models, but none look especially techy to my eyes.
Of course, when it comes to grots, conversion is always a great way to get the right-sized models with the right equipment