Show which size chart you want to assign to which product?
For example:
- Size chart for Gloves
- Size chart for jackets ....
and you want to make the minimum code change possible to your magento core files.
Here is the solution.
Method 1:
Create new attribut called "size_chart_template":
Go to Admin->Attributes->Manage Attributes
Add new attribute with the following properties:
For Frontend Properties: No everywhere and Position to 0
In Manage Label/Options:
Admin : Size Chart Template
add your options for example:
Helmets
Gloves
Jackets ...
Save your attribute.
Now go to Catalog->Attributes->Manage Attribute Sets
Select your set and add the attribut you have just created. (drag and drop)
Now we are going to assign for the product Red Helmet the size chart Helmets.
Go to Red Helmet and select Helmets from your dropdown list (You should add this attribut before use it).

<?php
if($_product->getAttributeText('size_chart_template') != ""){
$sizeChartURL= $this->getSkinUrl('sizecharts/'.$_product->getAttributeText('size_chart_template').'.php');
$sizeChartIcon= Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA)."size-charts/size-chart.gif";
echo '
';
}
?>
Now create skin/frontend/default/yourtemplate/sizecharts/Helmets.php
<?php
chdir ('../../../../../');
require_once getcwd().'/app/Mage.php';
umask(0);
Mage::app();
$mediaURL= Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA);
?>
Your HTML code here.
If you have any question do not hesitate to ask.
Method 2: Create Magento Size Charts Using Static Blocks and Javascript