I've not brewed with it, but from the Weyermann specs, it's
- 13L (11.8-13.7L)
- mild, restrained notes of caramel
- honey-colored hue
- use up to 30% in Belgian Blonde, Amber, Tripel, Dubbel
Given that it's 500g and it's playing against Vienna, the color is probably less significant than the flavor. To get the restrained caramel, you could probably get away with a very light crystal malt, such as CaraPils or Briess Crystal 10 to get a restrained caramel note and flavour. You could also look into doing a mix of 70% Crystal 10 and 30% Crystal 20 to get and a touch more caramel and closer the 13 L color.
This substitution chart shows comparable malts from different malters. It lists these malts as substitutes:
Crystal 10 Caramalt Carapils CaraMalt CaraHell / (CaraBelge) Light Carastan Light Caramel Carapils Caramel Pilsen
(Some malters produce malts with the same name, hence the duplicates.)