Im not talented but I'll give it a try. I couldnt find it on the internet either so I would just go off the second image you provided. If you have Photoshop or gimp it should be pretty straight forward to do yourself. Do you want it to be a flotilla emblem or an award emblem?
What I do is open an existing emblem in photoshop to get the image dimensions. U-67 was in 2nd flotilla, for example. That image is the data/emblem/flotilla folder. That image is 64x64 pixels. The background color will be transparent which I think in this case is grey. I then opened the image you provided and used a select wand to paint the star red with touch up using the paint brush. Then I used a white paint brush to remove "u-67" and the shading around the ram. Going back to the 2nd flotilla emblem I get the color of the background and set it to the photoshop's foreground color. Then I go back to the custom emblem and use the select wand to select all the white space background and fill it with the new foreground color.
Then I resized the image to 64x64 and dragged it overtop the open 2nd flotilla emblem and merged layers. This helps with getting the correct compression or whatever (24bit I think). Then save it with a new filename.
You can do the same process using a different existing emblem which may have different dimensions. You can also do a better job with editing the image. If you use it as a flottilla emblem, you define the emblem in the flotilla.cfg file in the cfg folder. I don't know about the award emblems though.
I have saved it as u-67.tga here:
http://www.danreavey.net/files/u-67.tga
NOTE: What the crap happened to my profile picture?