The 40.5mm Blue IR/NDVI Lens Filter from Kolari Vision works with full spectrum cameras to transmit both blue and IR, making it ideal for NDVI crop analysis applications. It allows an NDVI to be generated from a single image using the blue and red channels of the image. This filter is also useful for landscape photography, as it produces a similar effect to a 590nm IR filter after a channel swap, right out of the camera. This standard version of the filter features uncoated glass and an aluminum ring. (An optional pro version is available that has coated glass and a brass ring.)
A full spectrum modification is required to be made to your camera. This entails manually removing the camera's low-pass filter and replacing it with a clear filter. Once that's done, this filter will work as intended. (Kolari Vision can make the modification for you at a cost if you send in your camera to them.)