for the Visions in Fantasy range:
Excalibur Miniatures is a German company founded in 1982 as an importer of minis into Germany, but started producing their own figures in 1984. As of January 2015 there is a notice on their website that they don't produce miniatures at the moment, and are only selling off old stock. Excalibur produced no Ratmen to speak of, but they did have a figure riding a giant rat mount that could be of use:
Johnny Borg Castings is what's left of the late and much-lamented Mega Miniatures (R.I.P. 2001-2013). The single relevant figure available is a Ratman zombie, part of the Salvage Crew science fiction range.
Mierce's Darklands range features a race of Ratmen known as The Vras, some of whom originated in the Bane Legions game. Their range got a recent boost in a Kickstarter, but many of these are so far only represented on their website through concept art. Unlike in many cases, however, with Mierce one can reasonably assume the finished models will match or even surpass the art designs.
Just came across a few WIP shots of the new Mierce Vras units, worth sharing:
Located in Cambridge, UK, Otherworld Miniatures is a small company devoted to recapturing the nostalgia of old school fantasy roleplaying. They offer a 2 pack of Wererats sculpted by Matt Bickley as part of their Wilderness Encounters range.