I’ve used DC Fix on several lights and have always been very happy with the results. Purchased from Boaz here: DC-Fix Diffusion Film Sale
Never used the Lee filters, but might try them out. I also found this on their site:
“How do I attach my filters to some Perspex / window etc?
This largely depends on the application and final effect wanted, but an easy way is double sided sticky tape.
It is also possible to fix our standard product using water. It is not adhesive, but an experienced gaffer may be able to ensure that this holds in position, using the following method.
Clean glass / window thoroughly
mix tiny amount of detergent (washing up liquid) with water in a spray bottle
spray glass / window with mixture
apply lighting filter to glass / window
use a rubber window wiper to squeeze excess liquid out”
Also check this out, you input the source CCT and the desired CCT, and they recommend a specific product to create this effect: