I was in the same boat. it may be worth looking at the X7 lens case - that's available from DJI resellers as a part and it's essentially the same case. It just requires the internal foam replacing/trimming to suit the X5s.
I contacted DJI for a box, but it was around £125 with shipping, which I couldn't justify
EDIT: Apologies, just noticed we're talking about the X5 rather than the X5s. The suggestion still stands though - I think the X5 and X5s/X7 lens cases are pretty much the same externally