Use your digital camera, put the test in sunlight and take a picture without the flash.
( Would also find the paper from the day you got the positive and put that under the test, with the dates showing and a bit of headlines... fun for the scrap book!)
And then, if you really really want the test to show someone or whatever:
Print the photo, getting it a close to life size as possible.
Get a new , clean, un-peed on test.
Cut out the double line of the photo and put it into the test area of the new test.
Not the same, I know, but then your family is not holding somehting you peed on! (Not that that is not a funny thought when it come to most mother-in-laws but still!)
I have no idea about the actual test, but this should help!