I'd suggest contacting Daz direct to see if they have their old product archived and available for purchase - it was taken out of the store ages ago but turned up in a freebie pack if I'm not mistaken. Ask them if it comes with a texture map (but be aware it dates from a pre-HiRez era like the Daz Chimp which has awful lo-rez textures)

A good quality, morphable, acurate Rat figure is one of those Poser products that needs to be made.

Cheers