I need to find a source to purchase white velcro tape that is ideally
3/8" wide or at most 1/4" wide.  I have found black 1/4" velcro
mounting tape which is the closest to what I want.  This product needs
to have adhesive backing for both the hoop and hook section of the
tape.  I have found wider tape but found it is impossible to cut it
since the adhesive gums up the scissors. ...

If it helps you, my application and need for this tape is as follows: 
I live by the ocean and have white window screens.  The little metal
tabs that keep the screens in place rust out after a year.  I want to
buy a small roll at first to try it out, and if it works I will need
about 200 feet of it.

Thanks in advance for helping me find this product.

pbmaise,

I've got your velcro for you! 3/8 inch while velcro in a strip form,
25 yard rolls, so you'd need 3 of them

Hook side $29.00 a roll

Loop side $24.00 a roll.

You can order it from Mayer Johnson
http://www.mayer-johnson.com/dispmatls/Shtprot.html

There you go, good luck with your screens.

Nenna-GA
Google Answers Reseacher

Google search used was 
3/8  white velcro
://www.google.com/search?num=100&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&c2coff=1&q=3%2F8++white+velcro&btnG=Search

Thanks for your quick help and it is affordable too!  Very happy camper.

I'm glad you're happy with GA and myself. I hope you continue to use
our service, and I want to thank you personally for your rating.

Once again,
Nenna-GA
Google Answers Researcher

Try www.wbcindustries.com for their "off-brand" or "in-house brand"
hook & loop with adhesive.