Borrow a sewing machine. Watch some videos on line and have a go at making one yourself. I did and although a bit time consuming I ended up with a great fit. I’ve made a few for my friends and my other bikes.
It’s a great skill to learn.
The problem with the five is the shock goes across the frame so it doesn’t leave a lot of room.
I’d make a template first and then work out what you can get in that space and decide if it’s worth it before paying for alpkit to make one.
I’d also Google to see what others have done with a five frame. Have they made one for the top half and bottom half etc?
If you do decide to make your own and you need any pointers get in touch or go on the bearbonesbikepacking.co.uk website, there’s lots on there.
Good luck