I see - so it's coating and soothing the throat. Sounds like it would be easy enough to make something similar. Personally, I'd stick with the Aloe Vera gel, as the consistency is good, rather than faff about trying to make it from the plant. In the UK at least, you can get the gel for a couple of quid.

Honey might be a good addition, as its mildly antiseptic. (Warm water and honey is also a great thing to try).

However, do bear in mind that I'm not a qualified doctor, so take my advice with a pinch of salt. Also, this spray is only going to mask your symptoms, not cure them...