Scanned through some episodes and while I could have missed something these are the best images I could find of the model. I'm going to try making some simple drawings to work from because I think there are some distinct inconsistencies between this model and the drawings in The Spaceship Handbook.
The top and middle images are best for (relative) clarity. The bottom image shows better detail for the ray cannon affixed to the nose. I have another close-up of the full-size mock-up which shows quite a bit of rivet detail although I'm not sure whether I'll try to include that on my 3D model.
Like the TOS shuttlecraft there are inconsistencies between the full-size exterior and the miniature filming model. That leaves some room for interpretation as to what the "actual" ship should look like.