What size are your textures? I can see that there are four textures in total?
If that is the case, just place all of the textures inside one image twice the size of one of the single textures..........I confused myself with that sentence! WOW!
So, of the four textures you have in that folder, I am going to assume that each texture is 1024 x 1024. If this is the case, open GIMP or photoshop or paint.net (whichever you feel comfortable with); and create an image at the size of 2048 x 2048. This will give you he ability of all four 1024px textures into one.
Then, you will have to open your modelling software of choice and reassign the UV's to the new texture map. This will be easy as the model is already unwrapped. So, it will be a case of selecting each individual part and simply selecting all of the UV's for it, then resize them until they fit over the corresponding section of the new larger texture.
I have to apologise. When I read what you wanted to achieve I instantly thought, "Hey, I know what to do here, I can help", but, I REALLY struggled to get my words in any sort of order!
I hope this helps and doesn't confuse the matter further!
Cheers
Jay.