I was a bit skeptical (usually am) so I came up with my poor man's idea using an old expired insurance card. Its flexible and thin and coated which should make it somewhat oil resistant...
Leaking Seal Before

Modified card to insert (not sure why this pic came out smaller?)

Card inserted into fork

How did it work? When I did the Seca II, and I'll be damned it fixed it! On the old cafe racer (1975) used as a demo in the above pics, it did not. It did slow the leak so it did some good. I guess that bike's seal is just too old and too far gone so it will need to be replaced. Given my success rate of 50%. I think it is a worthwhile tool to buy. BTW My old insurance card only lasted one or two tries as it became oil soaked. Survived long enough to do the job. I am going to buy the "real deal" and try it again. Heck if it saves replacement of just one seal it pays for itself!