You can’t, but think about it for a second – the reason it is not protectable is because the individual parts have already been invented by someone else, and putting them together the way you did would be obvious to one skilled in the trade. ….
In a case like this the ONLY thing you can do is be first to market. Others will come behind you eventually anyway, so you just have to settle into that fact and decide if your lead time can make you enough money to make it worth your while.
I’m not being mean, it’s just the way it is when you develop something that cannot be protected. In that case you should file a PPA anyway, so you can use the term "patent pending" and help ward off some competitors.