There is now an actual product for modifying old sports jersey nameplates - SBNation.com
Personalizing Jerseys of Top N.F.L. Picks Is a Race Against the Clock - The New York Times
Jersey Nameplate - Etsy
Name Plate for Jersey-NamePlate
Jersey Framing and Memorabilia Custom Framing
Amazon.com: Custom Name Stitched for Football Jersey Any Your Name Design Personalized Nameplate Back Customization Your Team&Name Training Uniform Men : Arts, Crafts & Sewing
Pro Team STITCHED Nameplate - $39.99 : Professional Sports Lettering & Numbers, 100% AUTHENTIC TACKLE TWILL Athletic Numbers
Jersey Sports Box - Custom with Team Logo or Name Plate – Hi Impact Sports
SimStitch Twill Name Bars for Sports Jerseys | Stahls'