CD is right, coffee filters work just as fine, so do many white plastic object laying around that can be placed just as easily in front of the lens.
If you TRULY care about color management put the money instead toward a x-rite product such as color checker passport and make sure your monitor is calibrated correctly and often.
I think the passport was $99 when I bought it and it is simple, place in one test shot, then after import in LR for example, can set CUSTOM color profile for the shoot itself, and not only nail the white balance but also calibrate for all the colors too. Then all the images in that particular shoot under the same lighting conditions are instantly corrected as best can be done for the price. If lighting conditions change just put passport in for another test shot, and repeat. Take a minute to do it and then NO guessing about white balance and whether the colors were captured correctly.
Also, should point out the new product Photo Ninja from www.picturecode.com
It is similar to LR in being a RAW converter and editor for RAW, TIFF, and JPG. It offers something that LR doesnt' however. You can place color checker, gray card, etc in the shot, then tell it to do the same thing as the Xrite software does, but doesn't require the Xrite software, it is built into the Photo Ninja software itself. Pretty cool. So if know of where you can get the Color checking card, or Grey card, but don't want to shell out for the software then you can use Photo Ninja. ALSO, it comes with Noise Ninja, yep, can't beat that.
It can be downloaded as beta for long term use, just think the "save" function is crippled, think the price is $99, so if already have LR just get the color check, if thinking of LR and color checker save and get PN. Noise Ninja is worth another $100 by itself.
I saved an image of a Munson color card with the CMYK or LAB values for each square so you could use it to test your monitor's display of color, already have the color checker passport so never bothered to print it out to use as one. If CyberDyne or another guru thinks it could be of use after being professionally printed on proper paper with proper ink I will go and find it in my archives. It was given away freely in an old tutorial on color management, and doesn't list copyright nor did it mention restriction of use. It was a very very obscure article so just lucked out in finding it a long time ago.